Hhh ;: 








Gass. 
Book. 



Works by the same Author. 
THE HAND-BOOK OF HOUSEHOLD SCIENCE. 

A Popular Account of Heat, Light, Air, Aliment, and Cleansing, in their Scien- 
tific Principles and Domestic Applications. Designed for the Use of Schools. 
12mo. Illustrated. 450 pages. Price $1.50. 

This work has been prepared to meet a long-acknowledged want in our schools. 
There is a strong and growing demand for that kind of knowledge which can be 
made available in the daily operations of familiar life. "Various books have been 
prepared which cross the field of domestic science at different points, but this is 
the first work that traverses and occupies the whole ground. 

THE CHEMICAL CHART. 

On Rollers, 5 feet by 6 in size. New Edition. Price $6. 

This popular work accomplishes for the first time, for Chemistry, what maps 
and charts have for geography, geology, and astronomy, by presenting a new and 
valuable method of illustration. Its plan is to represent chemical composition to 
the eye by colored diagrams, so that numerous facts of proportion, structure, and 
relation, which are the most difficult in the science, are presented to the mind 
through the medium of the eye, and may thus be easily acquired and long re- 
tained. 

THE CHEMICAL ATLAS: 

Exhibiting the General Principles of the Science in a Series of Beautifully Colored 
Diagrams, and accompanied by Explanatory Essays. Large Quarto. 105 
pages. Price $2.50. 

The Atlas is a reproduction (in book form), and a continuation of the mode of 
exhibiting chemical facts and phenomena adopted in the " Chemical Chart." The 
application of the diagrams is here much extended, occupying thirteen plates, 
printed in sixteen colors, and accompanied by 100 quarto pages of beautifully 
printed explanatory letter-press. 



\ v 



..> x --- 



A CLASS-BOOK 



OF 



CHEMISTRY, 



THE LATEST FACTS AND PRINCIPLES OF THE SCIENCE ARE 

EXPLAINED AND APPLIED TO THE ARTS OF LIFE, 

AND THE PHENOMENA OF NATURE. 



DESIGNED FOR THE USE OF COLLEGES AND SCHOOLS. 



A NEW EDITION — ENTIRELY REWRITTEN. 

WITH OVER THREE HUNDRED ILLUSTRATIONS. — 




0/ 

So 

BY 

EDWARD L. YOUMANS, M.D., 

ACTHOE OF 

"the chemical chart,''' "chemical atlas," "hand-book of household 
science," etc. 



'Man is the interpreter of Nature— Science its right interpretation? 



NEW YORK: 
D. APPLETON & COMPAOT, 443 & 445 BROADWAY. 

LONDON: 16 LITTLE BRITAIN. 
$ 1863. 



my 



.y^t. ;?./&? 






w v 



•V 



Entered, according to Act of Congress, in the year 1863, by 

D. APPLETON & CO., 

In the Clerk's Office of the District Court of the United States for the 

Southern District of New York. 



2 3 



u & 



T O 

MY SIS TEE, 

MY COMPANION, INSPIRE It, AND ASSISTANT 

AMID 

PECULIAR DIFFICULTIES OF EARLY STUDY, 

AS A MASK OF 

AFFECTIONATE ESTEEM 
A2JD 

EVER-DEEPENING GRATITUDE 



PKEFACE. 



The Class-Book of Chemistry published some ten years 
ago has been rewritten, reillustrated, and much enlarged, 
and now appears as essentially a new work. Its aim is to 
present the most important facts and principles of the 
science, in their latest aspects, and in such a manner as shall 
be suitable for purposes of general education. 

So rapid is the progress of Chemical Science, that a 
book upon the subject, however faithfully it may represent 
the state of knowledge at the time of its publication, re- 
quires frequent and thorough revision. The past ten years 
have been remarkably fruitful in new facts and principles 
bearing upon Chemistry, the most important of which will 
be found embodied in the present volume. 

New views of the nature and connections of the forces 
have been accepted in the scientific world, which compel 
a new treatment of this branch of the subject. The old 
notion, that the forces are separate and peculiar forms of 
imponderable matter, has given way to the idea that they 
are closely allied and mutually convertible forms of activity 
or motion in ordinary matter. The older views are held 
to be self-contradictory, and as they do not explain and 
cannot represent the present facts of science, they are 
abandoned by the body of advanced scientific thinkers 
of the present time. The newer doctrines may be still 
incomplete, and are not without their difficulties, but they 
are more simple and rational ; they harmonize with the 
later facts of discovery, and open many new paths of in- 
vestigation of the highest interest and promise. 

An earnest desire to make this book a faithful reflex 
of the present state of Chemistry, and its connected ques- 
tions, has led to the adoption of the more recent views, 



6 PREFACE. 

and . to a much fuller treatment of Chemical Physics than 
was contained in the earlier editions of the work. It may 
be proper here to remark that the author has taught these 
views for several years in his lectures on the ' Chemistry 
of the Sunbeam ; ' the section placed under that title in 
this volume touching only a single branch of the discus- 
sion. 

The work will be found to embrace also other subjects 
of recent investigation : as Spectrum Analysis and the 
elements discovered by it ; Prof. Graham's interesting 
views of Dialysis and the colloidal condition of matter ; and 
Berthelot's remarkable researches in organic synthesis, 
or the artificial production of organic substances, together 
with various other particulars of scientific progress which 
are not to be found in contemporary text-books. 

The present work is not designed as a. Manual for 
Chemists. To such vast proportions has the science grown 
that voluminous and constantly enlarging treatises are pub- 
lished upon each of its numerous branches. A school text- 
book can therefore be but a brief compend of general 
principles and their most important applications, and is 
not to be judged by the completeness of its details, or its ful- 
ness as a work of reference. In this volume descriptions 
of those chemical substances which are not frequently met 
with, as the rare metals, are omitted, and directions for 
making experiments have been much condensed. By this 
means space is gained to treat with unusual fulness the 
more familiar objects of nature, as oxygen, air, water, food, 
&c, and to introduce much new and interesting informa- 
tion. 

Chemistry is not now what it was a few years ago — a 
mere matter of acids and alkalies, colored fires, and gas 
explosions, beginning and ending in the lecture room. It 
is an unfolding of the great laws of Nature, around and 
within us, and has an interest, not for experimenters alone, 
but for all who care to understand anything of the scheme 
of being which the Creator has established, and in the 
midst of which they are placed. The Class-Book is there- 
fore designed for the wants of that large class, both in and 
out of school, who would like to know something of this 
interesting science, but cannot pursue it in a detailed and 
experimental way. Its copious illustrations will partially 
supply the lack of experiments, but lectures and demon- 



PREFACE. 7 

strations are always invaluable whenever they can be ob- 
tained. 

While the application of Chemistry to the most im- 
portant arts has been duly noticed, more than usual atten- 
tion has been given to the Chemistry of Nature. The order 
of subjects has been so presented as to unfold the order of 
forces in nature — what may be reverently termed the divine 
logic of her activities. In the First Part are considered 
the great natural forces by which matter is moved and 
transformed ; in the Second Part, the application of these 
forces to the lower or mineral world, and the change of 
properties which they produce in inorganic bodies. Part 
Third treats of the organic kingdom, which rises out of the 
preceding, with the composition and changes of organic 
substances. In Part Fourth we see the completion of Na- 
ture's scheme in the world of life. The facts and prin- 
ciples of the three former divisions are here applied to the 
illustration of Physiological Chemistry. 

In preparing the volume the author has kept constantly 
in view that Chemistry is not only a branch of education to 
be acquired, but that it is a means of education — a valuable 
instrument of intellectual culture. His aim has been, not 
only to present important information but to arouse the 
mind and awaken a spirit of inquiry. He has striven to 
carry the thoughts upward to those larger and nobler 
views of scientific truth w T hich are more and more clearly 
revealed by the advance of inquiry, and w T hich are fitted 
not only to expand the thoughts, but to awaken the best 
emotions of our nature. 

A brief statement of the relations of science to the 
mind is made in the Introduction. The subject pertains to 
Mental Philosophy ; but many will study Chemistry wiio 
have not taken up that subject, and it is thought, that to 
such, the suggestions offered may prove serviceable. Should 
teachers think it too abstract and difficult for beginners in 
Chemistry, it may be passed by. 

In preparing this volume the author has resorted to 
various authentic sources of information ; but the second 
edition of Prof. W. H. Miller's excellent ' Elements of 
Chemistry ' has been taken as the chief guide in revising 
chemical data. Several passages have been transferred, 
with slight changes, from the i Household Science ' to 
Part IV. 



8 PREFACE. 

The author would acknowledge especial indebtedness 
to the new ' Lectures on Heat ' by Prof. Tyndall, which 
contains an able and attractive exposition of the new views 
of heat and its connections with the other forces. He is 
happy in being able to state . that this valuable work has 
been republished in this country, and he would earnestly 
recommend it to all teachers and students who take an 
interest in natural science. 

He would also renew his expressions of obligation to 
the writings of Dr. J. W. Draper, of New York, a gentle- 
man who stands alike distinguished in the field of original 
scientific research and of high philosophic thought. 

Grateful for the kindness with which former efforts 
have been received, he would indulge the hope that the 
present may be found still more worthy the confidence of 
the friends of education. 

New York, June, 1863. 



TABLE OF CONTENTS. 



PAGE 

Introduction, ........ 15 

PART I. 

CHEMICAL PHYSICS. 
CHAPTER I. 

OF SOME PHYSICAL CONDITIONS OF MATTER. 

§ I. Matter and Force, . . . . . . .27 

§ II. Gravity and Weighing, ..... 29 

§111. Comparative Weight— Specific Gravity, . . . .31 

§ IV. Minute Constitution of Matter, .... 35 

§ V. Molecular Attractions, . . . . . .38 

§VI. Solution, 44 

§VII. Crystallization, ....... 46 

CHAPTER II. 

CHEMICAL FORCES, LAWS, AND LANGUAGE. 

§ I. Chemical Attraction, ...... 55 

§ II. Laivs of Chemical Combination, . . . . .60 

§111. The Atomic Theory, . . . . . 64 

§IV. The Nomenclature — Chemical Language, . . . 66 

CHAPTER III. 

ELECTRICITY. 

§1. General Considerations, ..... 72 

§ II. Magnetic Electricity — Magnetism, . . . . .73 

i* 



10 CONTENTS. 



PAGE 



§ III. FranHinic Electricity— Electro-Statics, ... 76 

§ IV. Voltaic Electricity — Electro- Dynamics, . . . .83 

§Y. Effects of Voltaic Electricity, 93 

§ VI. Electro- Magnetism, . . . . . .96 

§VII. Thermo- Electricity, ...... 98 

§ VIII. Animal Electricity, ...... 101 

CHAPTER IV. 

HEAT. 

§1. Thermal Expansion— Thermometers, .... 103 

§11. Nature of Heat, 107 

§111. Sources of Heat, 110 

§ IV. Conduction and Convection of Heat, . . ' . .114 

§ V. Latent Heat— Interior Work, ..... 117 

. §VI. Liquefaction — Freezing— Ebullition, . . . .121 

§VII. Valorization, . . . ... . . 125 

CHAPTER V. 

LIGHT — THE RADIANT FORCES. 

§ I. Movements of Light, ...... 132 

§11. The Wave Theory, 135 

§ III. Thermal Radiations, . . . . . 139 

§ IV. Interference of the Radiants, ..... 148 

§ V. Polarization of Light, ...... 150 

§VI. Spectrum Analysis, . . . . . .154 

§VII. Chemistry of Light, ...... 158 

CHAPTER VI. 

MUTUAL RELATIONS OF THE FORCES. 

§ I. Connection of Polarities, . . . . . 164 

§ II. Connection of the Radiant Forces, ..... 166 r 
§ III. Conservation of Force, ...... 169 

PART II. 

INORGANIC CHEMISTRY. 

ORIGIN OF THE SCIENCE — ALCHEMY. 

CHAPTER VII. 

THE ATMOSPHERIC ELEMENTS. 

§1. Oxygen, . . . . . • • .181 

§11. Ozone — Allotropic Oxygen, ...... 190 



CONTENTS. 1 1 

PAGE 

§111. Hydrogen, ........ 192 

§ IV. Compounds of Oxygen and Hydrogen, .... 196 

§ V. Nitrogen and its Compounds, ..... 206 

§VI. Carbon, ........ 212 

§ VII. Compounds of Carbon and Oxygen, .... 21S 

} VIII. Compounds of Carbon and Hydrogen, .... 221 

§ IX. Compounds of Carbon and Nitrogen, .... 225 

CHAPTER VIII. 

THE ATMOSPHERE. 

§ I. Its Physical Properties, ...... 226 

§ II. CJiemical Constituents of the Air, . . . . .229 

CHAPTER IX. 

COMBUSTION AND ILLUMINATION. 

§1. Historic Notice— Phlogiston, ..... 233 

§ II. Combustion and Heat, ...... 235 

§ III. Flame and Illumination, . . . . . 238 

CHAPTER X. 

THE HALOGENS, OR SALT FORMERS. 

§ I. Chlorine and its Compounds, ..... 245 
§11. Bromine — Iodine — Fluorine, . . . . .252 

CHAPTER XI. 

THE PYROGENS, OR FIRE PRODUCERS. 

§ I. Sulphur and its Compounds, ..... 255 

§ II. Selenium and Tellurium, ..... 262 

§ III. Phosphorus and its Compounds, ..... 262 

CHAPTER XII. 

THE HTALOGENS, OR GLASS FORMERS. 

§1. Silicon and its Compounds, ..... 266 
§11. Boron, 269 

CHAPTER XIII. 

THE METALLIC ELEMENTS. 

§ I. General Properties of the Metals, .... 269 

§ II. Theory and Constitution of Salts, ..... 272 



12 CONTENTS. 

CHAPTER XIV. 

METALS WHICH DECOMPOSE WATER AT ORDINARY TEMPERATURES. 

PAGE 

§ I. Metals of the Alkalies, . . . . . ' . 277 

1. Potassium and its Compounds, .... 277 

2. Sodium and its Compounds, .... 281 

3. Manufacture of Glass, ..... 284 

4. Caesium— Rubidium— Lithium — Ammonium, . . 287 
§11. Metals of the Alkaline Earths, . . . . .289 

CHAPTER XV. 

metals which decompose water at a red heat. 

§ I. Aluminum and its Compounds, .... 293 

§ II. Iron and its Compounds, . . . . . . 296 

§111. Manganese— Nickel— Zinc— Cobalt— Cadmium — Tin, . 304 

CHAPTER XVI. 

METALS WHICH DO NOT DECOMPOSE WATER. 

§1. Chromium — Arsenic, ...... 307 

§11. Antimony — Bismuth — Copper — Lead,. . . . 309 

§111. The Noble Metals, 312 

CHAPTER XVII. 

SEQUEL TO THE METALLIC ELEMENTS. 

|I. Alloys, 317 



§11. Chemistry of Photography, . . . . .318 

PART III. 

ORGANIC CHEMISTRY. 
CHAPTER XVIII. 

CHEMICAL NATURE OF ORGANIZED BODIES. 

§ I. Recent Progress of the Subject, ..... 321 

§ II. Constitution of Organic Compounds, .... 324 

§ III. Colloid Constitution of Matter — Dialysis, . . . 327 

§ IV. Organic Analysis, ....... 329 

§ V. Theory of Compound Radicles, ..... 332 

§ VI. Homologous Series, ....... 833 

§VII. Theory of Types, 335 



CONTENTS. 13 
CHAPTER XIX. 

THE SACCHARINE AND AMYLACEOUS GROUP. 

PAGE 

§1. The Sugars, 338 

§11. Starch, 340 

§111. Woody Fibre, 342 

§ IV. Destructive Distillation of Wood, .... 344 

§ V. Decay of Wood and its Products, ..... 345 



CHAPTER XX. 

THE OLEAGINOUS GROUP. 

§ I. Fats and Fixed Oils, . . . . . .349 

§11. The Drying Oils, 351 

§111. The Unctuous Oils, ...... 352 

§ IV. Volatile or Essential Oils, ...... 354 

§ V. Resinous and Waxy Compounds, .... 356 

§ VI. Action of Alkalies upon Oils— Soaps, . . . .359 



CHAPTER XXI. 

ORGANIC ACIDS, BASES, AND COLORING PRINCIPLES. 

§ I. Vegetable Acids, ....... 361 

§ II. The Organic Bases, ....... 364 

III. Organic Coloring Principles, ..... 366 

CHAPTER XXII. 

NITROGENOUS COMPOUNDS — THEIR CHANGES AND EFFECTS. 

§ I. Ttte Albuminous Compounds, ..... 370 

§ II. Putrefaction and Disinfection, .... 373 

§111. Fermentation, ....... 376 

§ IV. Alcohol and its Derivatives, ..... 381 

CHAPTER XXIII. 

ANIMAL PRODUCTS. 

§ I. Animal Structures, ....... 385 

§11. Animal Secretions, ...... 389 



14 CONTENTS. 

CHAPTER XXIV. 

CHEMISTRY OF FOOD. 



PAGE 



§ I. Chemistry of Bread Making, . . . . . 392 

§ II. Culinary Changes of Alimentary Substances, . . . 395 

CHAPTER XXV. 

CHEMISTRY OF SOILS, . . . . . . . .399 



PART IV. 

PHYSIOLOGICAL CHEMISTRY. 
CHAPTER XXVI. 

VEGETABLE CHEMISTRY. 

§ I. Chemical and Vital Forces, ..... 404 

§ II. Germination and Cell Growth, ..... 405 

§ III. The Chemistry of Vegetable Growth, .... 408 

CHAPTER XXVII. 

DYNAMICS OF VEGETABLE GROWTH. 

§ I. The Forces of Organization, ..... 414 

§11. Chemistry of the Sunbeam, . . . . .418 

CHAPTER XXVIII. 

ANIMAL DIGESTION. 

§ I. Changes of Food in the Mouth, ..... 423 

§ II. Changes -of Food in the Stomach, . 424 

§111. Third Stage of Digestion, 427 

CHAPTER XXIX, 

FINAL DESTINATION OF FOOD. 

§1. Animal Nutrition, . . . . . .431 

§ II. Respiration and Circulation, . . . . .436 

§ III. Production of Animal Heat, ..... 442 

§ IV. Production of Animal Power, ..... 445 

CHAPTER XXX. 

CYCLES OF ORGANIC NATURE, ...... 449 



THE 



CLASS-BOOK OF CHEMISTRY. 



INTRODUCTION. 

ORIGIN AND NATURE OF SCIENTIFIC KNOWLEDGE. 

1. In entering upon the study of science, it is desirable that the 
student should have clear ideas of the origin and nature of the 
kind of knowledge he proposes to acquire. There is a vague no- 
tion among many people that scientific knowledge is of a totally 
different nature from ordinary knowledge — that science and com- 
mon sense, if not opposed to each other, are at all events very 
widely separated. That there is a difference between these two 
forms of knowledge is true, but it is by no means of the kind 
usually supposed, and it will repay a little careful attention to 
learn in what it really consists. 

2. Knowledge Progressive.— To understand nature is the pre- 
rogative of the human mind, yet this work is so vast and difficult, 
and its results so precious to humanity, that it is given to no man 
or to no age fully to penetrate her mysteries. No subject — not 
the minutest thing — can be so exhausted that further thought 
and the insight of genius may not discover still deeper meanings 
aud more subtile relations. And thus the mighty labor becomes 
progressive; each generation receives its inheritance of knowl- 
edge, makes its own additions, and bequeathes the whole to its 
successor ; so that "We of the present stand as 

' The heirs of all the ages in the foremost files of time.' 

1. What is stated as desirable for the student of science? What common 
opinion is referred to ? 2. How does knowledge become progressive ? S. What is 



16 INTRODUCTION. 

§ 

3. Knowledge is thus a growth. It begins in the common 
information of the uncultivated ; it develops, and in its higher forms 
it is called science. All the sciences have had their origin in the 
first rude actions of ordinary minds, and have grown up by slow 
degrees. Thus the art of counting gradually grew into the science 
of numbers ; that of land-measuring into the science of geometry. 
The grouping of the stars into fantastic resemblances of animal 
forms by the shepherds of old was the germ of Astronomy, while 
the common facts of combustion, fermentation, and decay, have 
been slowly evolved into chemical science. But common knowl- 
edge does not change its nature in becoming science anymore than 
does a shrub in becoming a tree, nor can the line be found where 
one stops and the other begins. 

4. A Test of Science. — As the phenomena * of nature take place 
with perfect regularity, just to the degree in which we understand 
her ways we can anticipate her results. Science thus confers 
foresight ; according to its perfection it enables us to foreknow what 
will take place in the future. Astronomy is the most perfect of 
the sciences, and hence we are enabled to predict astronomical re- 
sults with absolute precision thousands of years before they occur. 
So also with chemistry, just to the degree in which we understand 
it can we foretell what will take place when certain elements are 
brought together. This prophetic knowledge or prevision, is the 
most rigid test of science. 

5. Yet the mind of a nursery child answers to this test as well as 
the intellect of Newton. As has been well observed, even its ac- 
quaintance with an apple has in it the rudiment of science. It sees 
a certain form and color, and it knows if it puts out its hand it will 
have certain impressions of roundness, smoothness, resistance, and, 
if it bites, a certain taste. Nor can anything be more certain than 
the previsions of ordinary minds ; for example, that unsupported 
bodies will fall ; that water will extinguish fire, and night succeed 
day. Familiar as these cases are, we see in them the rudiments of 



* The word phenomena signifies literally appearances ; they are objects seen or 
events taking place in the usual course of nature, and not things rare and extraor- 
dinary, as is sometimes erroneously supposed. 

science ? What is the origin of all sciences ? Examples ? 4. "What power does a 
knowledge of the order of nature confer? Examples? What is it called? 
5. What is said of the knowledge of the child ? Give examples of common previ- 
sions. What is said of them ? 6. What example is given of the previsions of 



ORIGIN AND NATURE OF SCIENTIFIC KNOWLEDGE. 17 

the highest science ; that is, a perfect accordance between the anti- 
cipated occurrences and those which actually take place. 

6. How Knowledge Grows. — We may trace this element 
through all the stages of the development of knowledge. A lad 
knows that the smoke, from the fire he is kindling, will rise; that the 
fire will consume the fuel and presently warm the room and boil 
water. These are previsions which he makes just as certainly and 
accurately as the philosopher. 

7. But when the mind begins to inquire, a new class of previ- 
sions is reached. It is seen that the fire will disturb the equili- 
brium of the air and thus cause the smoke to rise ; that an element 
of the air will enter into chemical union with the fuel ; that there 
will be no real destruction of matter, but only a change of its 
forms ; that the chemical action will give rise to heat which will 
be propagated by conduction through the iron, by circulation 
through the water, and by radiation through the air. These results 
are not different in kind from the first — no more positive or cer- 
tain ; but while the facts and relations in the first case are simple 
and obvious to the feeblest apprehension, in the latter they are 
more complex and obscure, and to grasp them requires a higher 
exercise of reason. 

8. But the evolution proceeds still higher ; at first there is only 
certainty ; at last there is exactness. First the hind* of effect are 
foretold, and then their amount. The weight and pressure of the 
air, the rate of its expansion by heat, the amount of its ascensional 
force, and how much the chimney retards by friction, are precisely 
determined ; and the consequent power of draft is predicted. Xot 
only that oxygen combines with the fuel, but exactly how much 
will be required to consume it, what quantity of heat will be gen- 
erated, how much water boiled, and space warmed, are finally fore- 
told. In its completest form Science advances to measurement : it 
first determines qualities, then quantities.* 

9. Thus is common knowledge constantly rising into the higher 
and more perfect form of science ; its tendency is ever from the im- 



* For an able exposition of the doctrine here glanced at, the student is referred 
to a paper in Herbert Spencer's Essays, entitled ' The Genesis of Science.' 

ordinary knowledge ? 7. What higher previsions may arise from these ? "What is 
the difference between them ? 8. What others are mentioned in the third stage of 
evolution? Give illustrations. 9. What is said of the mental operations which 



18 INTRODUCTION. 

mediate to the remote, from the loose and vague to the definite 
and exact. If now we examine those mental operations by 
which knowledge is developed we shall find them to be one and 
the same in all the degrees of its evolution. Mind acts according 
to its necessary laws, which are identical in the child, the adult, 
and the most advanced philosopher. 

10. Observation. — By the impressions produced upon the senses 
our attention is constantly solicited to the objects around us, and the 
giving of this attention is called observation. This is the basis of 
experience and the first condition of all ordinary knowledge. The 
person who carefully remarks the conduct and appearance of peo- 
ple, giving attention to their peculiarities and differences, is called an 
' observer of human nature.' And so the agriculturist who notes 
whatever pertains to soils, stock, fruits, &c, is known as an 'ob- 
serving farmer.' 

11. Science also begins exactly here; its basis is observation. 
But the hasty and careless observations of people in the ordinary 
affairs of life, where appearances are constantly misinterpreted and 
everything is seen in the light of preconceived ideas, would be a 
very insufficient foundation for science. Its first step, therefore, 
is to educate this faculty by a systematic discipline. Observation 
is not mere looking or listening ; it is discrimination. It is the eye 
of reason that observes. For purposes of science observations 
must be made with patience and caution ; numerous sources of 
error from without and within — sources of which people generally 
are entirely unconscious — have to be vigilantly guarded against, 
or the results are worthless. 

12. Experiment.— Here again we commence with the ordinary 
experience of mankind ; everybody makes experiments. "We wet, 
heat, scratch, bend, press, and tear substances to test their quali- 
ties. We try the fastness of colors by washing a fabric, and the 
genuineness of coin by its sonorous ring. But what is thus be- 
gun and practised in a rude way by everybody, science improves 
and carries out in a systematic manner. Its cultivators not 
only passively observe, but, with hand and instrument, in a thou- 
sand ways they put nature to direct trial. Objects are placed in as 
many different conditions as the operator's ingenuity can contrive, 

produce science? 10. What is observation? Mention common instances. 
11. What is the basis of science ? How does scientific differ from common obser- 
vation ? 12. What examples are given of common experimenting ? How does 



ORIGIN AND NATURE OF SCIENTIFIC KNOWLEDGE. 19 

and the changes noted and compared. Only by this assiduous 
cross-questioning of nature by thousands of investigators has our 
knowledge of her laws been enlarged in extent and increased in 
exactness until it has reached its present advancement. 

13. Diversity of Natural Objects. — The objects and operations 
of nature with which observation acquaints us are innumerable. 
Each region of the earth produces its peculiar forms of life ; each 
tree has its own appearance ; each leaf its peculiarity ; each ani- 
mal its distinguishing marks ; each stone its individual features. 
No two faces, no two blades of grass, and, as the microscope shows, 
no two grains of sand are precisely alike. So also with the oc- 
currences of experience. No season is like its predecessor ; no day 
repeats another ; no event is ever exactly reproduced. 

14. Abstraction, Generalization, Classification.— This vast mul- 
tiplicity of objects and events would confuse anct confound the 
mind if it attempted to grasp or remember them all. The facts 
must be grouped or bound together in bundles before the mind 
can command them for purposes of general knowledge. Observa- 
tion accumulates individual facts ; the mind then searches for some 
point or quality in which a great number of objects agree, and 
having found it, gives them a common name. Thus all animals 
having a spinal column were grouped together as vertebrates ; all 
trees which grow by the successive addition of external layers as 
exogens. 

15. As this act of the mind puts aside those particulars in 
which objects differ, and separates or abstracts those of resem- 
blance, it is called a process of abstraction: as it is a passing 
from particulars to generals, it is called generalization; while this 
sorting of a multitude of things into parcels for the sake of know- 
ing them better and remembering them more easily, is called classi- 
fication. 

16. But this is no peculiarity of science, for all minds inevit- 
ably proceed in the same manner. Were a basket of fruit placed 
before a child, it would very naturally separate and group together 
the apples, the pears, and the plums ; it would therefore perform 
the operations of abstraction, generalization, and classification. 

science improve upon this ? What is the result ? 13. What is said of the diversity 
of natural objects ? 14. What would be the effect of trying to remember them all ? 
What has to be done 1 Examples. 15. What is abstraction ? Generalization ? 
Classification? 16. What familiar examples are offered ? 17. Describe the ill us- 



20 LNTTKODUCTION. 

Were the chemical elements placed before it on a table, it would 
also naturally separate all the shining metals from the rest, and 
thus take the first great step in chemical classification. Those 
mental operations which are practised by everybody in an uncon- 
scious and imperfect way, give rise at length, by culture and dis- 
cipline, to comprehensive scientific methods. 

17. Induction. — This term denotes an essential operation of the 
mind, by which knowledge is acquired, and which is just as well 
exemplified in every-day experience as in the highest efforts of 
thought. For example, you place a piece of oak wood in the fire, 
and it burns ; you then put pieces of maple, pine, and mahogany 
in the fire, and they also burn. From these facts you gather the 
general principle that all wood will burn. This is called an induc- 
tion, from induco, to lead m, and signifies the bringing in of one 
fact after another to establish a general truth. It is true there 
are thousands of varieties of wood, and you have tried but three 
or four ; yet from your experience of nature you conclude that 
what is true in certain cases will be true in all similar cases. If 
you observe in a larger number of instances that wood burns, the 
induction is strengthened. 

18. Deduction. — If now you meet with a new variety of wood, 
you immediately think in the following manner, which is called a 
syllogism : All wood is combustible ; this substance is wood, and 
therefore it will burn. In this case you take the induction as a 
general principle, and apply it in a particular case. This is deduc- 
tion, from deduco, to lead down, and signifies the descent from a 
universal truth to a special application. Thus induction discovers 
principles, while deduction applies them. 

19. Verification is testing the truth of a conclusion. Should 
you hear various persons from different parts of the world assert 
that they have tried many kinds of wood, and find that they all 
burn, you would say this is an experimental verification of the law. 
Or if a chemist should say, I have analyzed many kinds of wood, 
and find that they all consist of the same combustible elements ; 
other chemists obtain the same results with other sorts, and as the 
mode of vegetable growth and the essential constituents of plants 
are everywhere the same, all wood must be combustible, you 

tration of induction. What does the word signify ? What is its basis? 18. If a 
new kind of wood is met with, how does the mind proceed ? What is deduction ? 
19. What is verification ? Describe the experimental and theoretical verifications. 



OEIGIN AND NATURE OF SCIENTIFIC KNOWLEDGE. 21 

would look upon this as a theoretical verification of your law. 
You would further say, this principle is true, because it may be 
verified by anybody at any time. 

20. The grandest discoveries in science are made in precisely 
the same way. The master minds of our race, by a course of 
toilsome research through thousands of years, gradually establish- 
ed the principles of mechanical force and motion. Facts were 
raised into generalities, and -these into still higher generaliza- 
tions, until at length the genius of Newton seized the great prin- 
ciple of attraction, which controls all bodies on the earth and in 
the heavens. He explained the mechanism and motions of the uni- 
verse by the grandest induction of the human mind. 

21. The mighty principle thus established now became the first 
step of the deductive method. Leveerier, in the solitude of his 
study, reasoning downward from the universal law through plane- 
tary perturbation, proclaimed the existence, place, and dimensions 
of a new and hitherto unknown planet in our solar system. He 
then called upon the astronomer to verify his deduction by the 
telescope. The observation was immediately made, the planet was 
discovered, and the immortal prediction of science was literally 
fulfilled. 

22. Hypothesis. — This is a supposition or guess put forth to 
account for any occurrence or state of facts. For example, a boy 
misses his knife. Various conjectures go rapidly through his mind 
as to the cause of its disappearance. He may have mislaid it, left 
it in another pocket, or it may be lost, lent, or stolen. Each of 
these ideas involves a hypothesis of the loss of the knife. These 
he proceeds to test one after another ; he examines his pockets, 
searches in various places, inquires of his companions, but cannot 
find it ; that is, each of his hypotheses fails when he attempts to 
verify it. At length, perhaps, it is found upon a comrade under 
circumstances which establish the hypothesis of its theft. Thus 
hypotheses, instead of being the mere fine-spun fancies of unprac- 
tical thinkers, as is too commonly supposed, are employed every 
day by everybody as the only guides of conduct and action. Lit- 
erally a hypothesis signifies a supposition placed under the facts as 
a platform to support them. 

20. What example is given of scientific induction ? 21. How was it applied deduc- 
tively ? How verified ? 22. What is a hypothesis ? Describe a familiar use of 
hypothesis. Of what essential use are hypotheses? 23. What is the literal 



22 INTRODUCTION. 

23. All scientific inquiry begins in the same manner with 
guesses. The facts being observed, various conjectures or hypo- 
theses are made to explain them. It cannot be denied that in 
science, as in common life, there are various aptitudes for making 
hypotheses which no precepts can teach. It depends largely upon 
boldness of thought and fertility of invention ; upon an original 
cast of the intellect — the questioning temper — the busy, suggestive 
mind — the piercing glance of genius, which sees what others over- 
look, which prizes what others neglect, which takes its flight 
beyond rules, and is a law to itself. 

24. Insufficiency of Hypothesis. — But it is not by skilful con- 
jecture that knowledge grows, or it would have ripened thousands 
of years ago. It was not till men had learned to submit their 
cherished speculations to the merciless and consuming ordeal of 
verification that the great truths of nature began to be revealed. 
Kepler tells us that he made and rejected nineteen hypotheses of 
the motion of Mars before he established the true doctrine that 
it moves in an ellipse ; and Dr. Faraday remarks : ' The world 
little knows how many of the thoughts and theories which have 
passed through the mind of a scientific investigator have been 
crushed in silence and secrecy by his own adverse criticism.' 

25. Theory means literally a view. It is an accepted hypothe- 
sis ; an explanation of phenomena. For example, the principles 
which explain the structure and movements of a watch form the 
theory of the watch. It is common to contrast theory with prac- 
tice, disparaging the former and commending the latter ; but this 
is erroneous. Theory is derived from practice ; indeed, it is a 
knowledge of the principles by which practice accomplishes its 
end. ^ 

26. Cause and Law. — Any agency which produces an effect, 
and which when known explains it, is termed its cause; while the 
manner in which the force acts in producing the effect is termed 
its law. Thus the cause of the fall of a stone is the force of gravi- 
tation, while the conditions under which the power acts is called 
its law ; viz., that bodies attract each other with a force directly 
proportional to their respective masses and inversely as the square 

meaning of hypothesis 7 "Where does scientific inquiry begin ? Upon what does 
skill in making hypotheses depend? 24. What beside hypothesis is necessary * 
to denote science ? What is said of Kepler ? What does Faraday observe ? 
25. What is a theory ? How is it related to practice ? 26. What is a cause ? What 



ORIGIN AND NATURE OF SCIENTIFIC KNOWLEDGE. 23 

of their distances. The cause of chemical combination is the force 
of affinity ; the law of the force is that bodies combine in definite 
and constant proportions. Strictly speaking, that which invariably 
precedes an act, its antecedent or several antecedents, constitutes 
its cause ; while such an expression of the condition in which the 
power acts, or the event occurs, as enables the result to be deter- 
mined beforehand, is known as the law. 

27. We may call the first conjecture of universal attraction in 
the mind of Xewton, which he believed probable, but held in sus- 
pense for many years, an hypothesis. But when important facts 
which apparently contradicted the hypothesis were revised and 
found to agree with it, it assumed the character of a theory, and 
as such it was on trial for a hundred years, until the greatest mathe- 
maticians, clearing away difficulty after difficulty, demonstrated it 
to be a universal law. 

28. Empiricism ordinarily signifies mere pretension and quack- 
ery, but in science it denotes the results of observation just as they 
are obtained, before they are reasoned upon or reduced to princi- 
ples. Empirical results of inquiry are the naked facts without any 
theorizing or attempts to explain them. 

29. Science and Art. — As science represents the later stage of 
knowledge, art represents the earlier. Men first, through painful 
toil, servile imitation, and blind rules, learned what to do ; then 
came the question ichy it was done, and the advance was made to 
theories and explanations, or science. Art is therefore empirical, 
science rational ; art asks for rules, science for reasons ; art is an 
affair of practice, science of principles and causes. The first is the 
root, the latter the outgrowth. The arts and sciences mutually 
help each other forward. Art presents to science her difficulties ; 
science solves them, and, while thus increasing her own stores of 
truth, returns to art principles for her better guidance. 

30. Why Science is so Recent. — For thousands of years the 
race lingered in the early or art-period of knowledge. This was not 
for lack of intellectual activity, but from its misapplication. The 
ancient philosophers, disdaining nature, retired into the ideal 
world of pure meditation, and holding that the mind is the meas- 

a law? Examples ? 27. What example is there of the growth of a hypothesis to a 
theory and how ? 28. "What is empiricism ? 29. "What are the relations of art and 
science ? "What did men first learn ? How are science and art constructed ? 
How do they help each other ? 30. "What was the state of mind of the ancient 



24 INTRODUCTION. 

ure of the universe, they believed they could reason out all truths 
from the depths of the soul. Despising matter, they were not 
drawn to observe and study ifc ; despising labor as menial and de- 
grading, they would not experiment ; consequently they lacked 
the first conditions of science, Observation, Experiment, and In- 
duction. They reasoned from fanciful notions to worthless con- 
clusions, and the intellectual power of ages was thus wasted. 
Genius spent itself in beating the air ; the philosophers wrestled 
with shadows ; they chased each other round the circles of verbal 
disputation, they pursued the rainbow, disdaining the priceless 
gems which abound in the earth beneath. It was the period of 
inexperience, and their mistake was perhaps natural, but it was an 
error that paralyzed the world. The first step of progress was 
impossible. There was no conquest of nature or liberation of man 
from the drudgeries of endless toil ; no spirit of general inquiry, 
no projects of education or hope of improvement. 

31. Succession of the Sciences. — Thus the sciences do not rise 
or advance together ; they have appeared in succession — the 
earlier, as it were, preparing for the later, and the later springing 
out of the earlier. Man was first impressed by the beautiful regu- 
larity of the celestial motions ; they excited his wonder and aroused 
his thought ; and hence Astronomy is the oldest of the sciences. 
Then the visible movements of earthly bodies were also found to 
be governed by invariable laws, and Mechanical science was the 
result. The human mind having now established the idea of 
order in the heavens and on the earth, it was next found that the 
deeper changes which go on within material objects, altering their 
nature and properties, are also of an invariable character; and 
then appeared the science of Chemistry ; and when, still later, the 
same thing was perceived in living beings, there arose the science 
of Physiology. 

32. Many subjects are now in the rudimental condition of 
common knowledge which are yet to assume the scientific form, 
while some are capable of only a partial development. Science 
furnishes the only true method of their study, while yet they are 
so complex that the human mind may never be able completely to 
analyze them For example, Commerce, Education, Society, and 

philosophers? "Why did they fail in science? What was the consequence of 
their attitude of mind ? 31. In what manner have the sciences appeared ? In what 
order ? 32. In what condition are many subjects at present ? What is said of 



ORIGIN AND NATURE OP SCIENTIFIC KNOWLEDGE. 25 

History are not properly to be considered as sciences ; yet the 
operations of business, the culture and growth of mind, the social 
relations of men, and the course of the world's events, inasmuch 
as they all unquestionably involve fixed principles and the action 
of uniform causes, must become more and more scientific in the 
method of their treatment. 

33. Claims of Science. — The idea thus briefly illustrated, that 
knowledge is by its very nature progressive — that it grows into 
the higher form of science through the education of the essential 
faculties of the common mind — is of the deepest significance in 
education. We see that science is not a mere curious and profitless 
prying into the obscure recesses of nature, nor a rigid system of 
thought inapplicable and worthless in the walks of common ex- 
perience. On the contrary, it is a result of the mind's normal 
growth — a product and proof of its completest discipline. By a 
gradual transition we rise from the obvious and simple to the re- 
mote and complex ; the same faculties being called into progres- 
sively higher and more systematic exercise in the ascending course 
of scientific inquiry. 

34. We observe, also, that science is not, as is often said, simply 
an affair of the material world, nor its progress a mere physical 
progress. All science is of the mind, and its progress mental, and 
whether thought be directed without, to material things, or turned 
within to study itself, the same intellectual operations are employ- 
ed. The progress of Chemistry, the advancement of Agriculture, 
and the growth of Physiology, are not outward things ; they are 
all conditions of thought. The mind moves forward, and the ex- 
ternal results are but the signals and registers of its march. 

35. And these results are of the mightiest import. The dis- 
coveries of Gravitation, of Oxygen, of the Circulation of the 
Blood, of Vaccination, Anaesthetics, and Photography — the inven- 
tion of the Mariner's Compass, of Gunpowder, the Printing 
Press, the Chronometer, the Steam Engine, and the Electric 
Telegraph, have reconstructed human relations ; they are steps 
of advancement in which the whole world is implicated. But 
great as are the material revolutions which they have produced, 
they have a more momentous significance as the first glorious fruit- 
ings of the growth of knowledge. They are witnesses of what 

their future? How are education and history to be regarded? 33. What is its 
relation to the mind ? 34. In what does the progress of science consist ? 35. What 
2 



26 INTRODUCTION. 

can be accomplished by the earnest, persevering study of nature ; 
they are prophetic of a new dispensation of the intellect — of a 
wider and nobler culture, in which the living universe of God 
shall neither be contemptuously passed by, nor assigned an inferior 
place in courses £>f study. 

36. The Demand of the Age.— We cannot better close these 
observations on the nature and influence of science, than with 
the following extract from Prof. Liebig : ' The great deside- 
ratum of the present age is practically manifested in the estab- 
lishment of schools in which the natural sciences occupy the most 
prominent place in the course of instruction. From these schools 
a more vigorous generation will come forth, powerful in under- 
standing, qualified to appreciate and to accomplish all that is truly 
great, and to bring forth fruits of universal usefulness. Through 
them the resources, the wealth, and the strength of empires will be 
incalculably augmented ; and when, by the increase of knowledge, 
the weight which presses on human existence has been lightened, 
and man is no longer overwhelmed by the pressure of earthly 
cares and troubles, then, and not till then, will his intellect, purified 
and refined, be able to rise to higher and higher objects.' 

is said of the great discoveries? What do they show? 36. What does Liebig 
state to be the requirement of the age ? What would be the effect of such schools ? 



PAET I. 
CHEMICAL PHYSICS 



CHAPTER I. 

OF SOME PHYSICAL CONDITIONS OF MATTER. 



§ I. Matter and Force. 

37. Matter. — Whatever occupies space and is revealed to our 
senses, is termed matter. Different kinds of it, as wood, water, 
air, are called substances ; and any limited portion of it is called a 
body. The properties of matter are the characters by which it is 
known ; and these may be either general, as those which belong 
to all matter, or specific, those which serve to distinguish one 
body from another. 

38. .Bodies are of two kinds, simple and compound. Compound 
bodies are such as can be decomposed or separated into simpler 
parts or elements. Simple bodies, on the contrary, cannot be 
thus separated. Water is a compound, and can be resolved into 
two invisible gases, but neither of these can be again decomposed. 
Brass may be separated into copper and zinc, but no one has yet 
been able to obtain from these anything besides copper and zinc. 

39. Persistence of Matter. — Matter is impenetrable. As it is 
created in space, it must occupy space ; two bodies cannot exist 
in the same place at the same time. Matter is thus persistent 
in space, and it is also persistent in time ; — it is indestructible. 

37. What is said of matter and its properties ? 38. How are bodies divided ? Give 
examples. 39. What can you say of the indestructibility of matter ? 40. G-ive ex- 



28 CHEMICAL PHYSICS. 

There is no evidence that in the course of nature, or by any of the 
operations of art, matter is either called into existence or anni- 
hilated. It may be changed from state to state thousands of times 
without the smallest loss. A pound of ice converted into water 
or into steam continues to weigh exactly a pound. "When fuel is 
burned, or water disappears by evaporation, or our own bodies 
are resolved into earth and air, it is only the migration of matter 
through the circle of natural transformations. Forms alone are 
destroyed — matter remains imperishable. 

40. Changes of Matter. — The universe is everywhere in mo- 
tion. The atmosphere is agitated by winds ; the world of waters is 
in perpetual circulation ; plants and animals spring from the earth 
and air and return to them again ; all substances around us are 
undergoing slow transformations ; the stony records of the strata 
are but histories of past revolutions ; our ponderous earth shoots 
swiftly along its orbit, while the mighty sun, with all his attendant 
planets, is sweeping on forever through shoreless space. Nothing 
around or within us is absolutely at rest. 

41. Force. — That which moves matter and produces change is 
called power, ox force. The causes of the foregoing changes are 
called the forces of nature. Thus the Force of Gravity draws a 
piece of iron to the earth ; Cohesive Force holds its particles to- 
gether ; Mechanical Force shapes it ; Heat Force melts it ; and 
Chemical Force rusts or dissolves it. Matter and force are insep- 
arable; we know nothing of force except through matter, and 
nothing of matter except by its forces. 

42. Physical Changes. — Those various alterations of place, 
form, and quality which bodies undergo without destroying their 
distinctive properties are termed 'physical changes. Thus iron 
may be cut into nails, rolled into sheets, drawn into wire, melted 
or magnetized, but through all these changes it still remains iron. 
"Water changes its form, becoming a solid or vapor, but its peculiar 
composition as water remains unaltered. Gravity, cohesion, light, 
heat, electricity, and magnetism are the forces chiefly concerned 
in producing these changes, and are therefore called physical 
forces. That branch of science which treats of their effects is 
termed Physics. 

amplea of the changes of matter. 41. What is force ? Mention the effects of va- 
rious forces. 42. What are physical properties ? Physical changes ? 43. What 



NATURE OF CHEMICAL CHANGES. 29 

43. Chemical Changes. — If iron be rusted, burned, or dis- 
solved, it undergoes another and a deeper change ; its peculiar 
properties are destroyed, and the metal disappears. In common 
combustion air and fuel are both changed, and new substances are 
produced. These are examples of chemical changes, such as are 
going on constantly around us ; indeed, nature is a vast laboratory 
where they are incessantly taking place up.on a stupendous scale. 
Chemistry considers the composition of matter, the nature of its 
elementary parts, the properties of the compounds formed from 
them, and the forces by which its various combinations and de- 
compositions are produced. 

44. Chemical Physics. — Physical forces and conditions have so 
powerful an influence over chemical action that some knowledge 
of them is indispensable to the chemical student. The progress 
of inquiry has, moreover, shown that the various forces are far 
more intimately related to each other than was formerly supposed, 
so that to understand them in the best manner they must be pre- 
sented together. Accordingly, under the title of Chemical Physics, 
we first treat of those physical agencies which are most intimately 
connected with the subject of Chemistry. 

§ II. Gravity and Weighing. 

45. One of the simplest facts of observation is that bodies are 
drawn down to the surface of the earth with power. The at- 
tractive force which produces this effect is called Gravity. It acts 
between masses of matter of every kind, and at all distances ; the 
earth, sun, moon, and all the heavenly bodies, thus influence each 
other. The various objects upon the earth's surface are not only 
powerfully attracted by the mass of our globe, but, in an infinitely 
lesser degree, they also attract it ; and it has been further demon- 
strated that they also attract each other. A pair of leaden balls 
two inches in diameter were attached to the ends of a rod which 
was suspended in the middle by a fine wire, Fig. 1. Two other balls 
of lead, a foot in diameter, were placed upon a revolving platform, 
and when the larger and smaller balls were brought near together, 
they were mutually attracted, as was shown by the motion of the 

is the peculiarity of chemical changes ? What does chemistry consider ? 44. "What 
has physics to do with chemistry ? 45. What is the effect of gravity ? Its extent ? 



30 



CHEMICAL PHYSICS. 



Fig. 1. 




rod. The force exerted did not exceed the twenty-millionth of the 
weight of the lesser ball, but was sufficient to slightly twist the 

wire, and give rise to a small oscilla- 
tory movement. The seemingly in- 
ert masses were thus proved to be 
alive with power. 

The force of gravity is propor- 
tional to the quantity of matter ; 
that is, if the earth had twice its 
present mass its attraction would be 
doubled, and if but one-half its mass, 
its force would be only half as great. 
So with any body on the earth, the 
force with which it is attracted in- 
creases or diminishes in exact pro- 
Mutual attraction of leaden "balls, portion to its quantity. 

45. This force gives rise to Weight. — If a body, instead of 
being allowed to fall, is supported, its tendency to descend is not 
destroyed. It is drawn downward with the same force, but as it 
is resisted, and at rest, the force takes the shape of pressure. 
This downward pressure of bodies is called their weight. The 
weight of a body is the force it exerts in consequence of its gravity, 
and, as this force depends upon the quantity of matter, it is clear 
that if the mass be doubled, the weight will be doubled ; if the 
mass be halved, the weight will be halved. Weights are therefore 
nothing more than measures of the force of gravity in different 
objects. Thus we discover the close connections and depend- 
encies of all things. The same force which controls the mighty 
system of celestial orbs, measures quantities of matter in the daily 
transactions of business life. 

47. Standard Weights. —The operation of weighing consists in 
estimating the force with which any given body is attracted 
toward the earth by comparing it with other masses of matter 
already weighed and marked according to some fixed standard, as 
Troy, Avoirdupois, or French weight. These standard scales are 
quite arbitrary, there being no natural starting-point, or unit. The 
grain weights were originally grains of wheat. The scales estab- 



Describe the experiment. To what is this force proportional ? 46. What is the 
cause of pressure ? What is weight ? 47. What are standards of weight ? How 



IMPORTANCE OF WEIGHING IN CHEMISTRY. 



31 



lished in this country are capriciously arranged, while the French 
employ a decimal scale, which is far more convenient, and is grad- 
t ually coming into use among men of science. 

43. Weighing Instruments. — The instruments employed in fa- 
miliar weighing are steel-yards, springs, and scales, or balances. 
The chemical balance, Fig. 2, used for analysis, consists of an in- 
flexible bar, delicately poised at a point exactly midway between 
its extremities, from which the scale-pans are suspended. Its beam 
rests upon a fine edge of hardened steel, which is supported by a 
flat plate of polished agate. This beam oscillates toward the 
earth just as the rod in the pre- Fig. 2. 

ceding experiment oscillated tow- 
ard the larger balls. Such a 
balance is as indispensable to the 
laboratory of the chemist as the 
telescope is to the observatory of 
the astronomer. The foundations 
of the science are numerical laws, 
which could never have been 
arrived at except by its means. 
Prof. Liebig says, 'The great 
distinction between the manner 
of proceeding in chemistry and natural philosophy is that one 
weighs, while the other measures. The natural philosopher has 
applied his measures to nature for many centuries ; but only for 
fifty years have we attempted to advance our natural philosophy 
by weighing. For all great discoveries chemistry is indebted to 
the balance, that incomparable instrument which gives perma- 
nence to every observation, dispels all ambiguity, establishes 
truth, detects error, and guides in the true path of inductive 
inquiry.' 

§111. Comparative Weight — Specific Gravity. 

49. Weight, as thus far noticed, involves only the simple idea 
of gravity, and is termed absolute weight ; it has no reference to 




The Chemical Balance. 



does the French differ from other weights ? 48. What is the construction of the 
chemical balance? How does chemistry differ from natural philosophy? What 
does Liebig say of the balance ? 49. How is bulk related to weight ? What cases 



32 CHEMICAL PHYSICS. 

bulk or volume ; yet bodies differ very much in their density, or 
the quantity of matter which they contain in a given bulk. Thus, 
a pound of cork exactly counterpoises a pound of lead, though the 
former occupies forty times as much space as the latter. So 100 

cubic inches 

Pounds. Grains. 

Of Hydrogen weigh ... 2.14 

"Air "... 31 

"Water, " ... 3.604 

" Iron "... 28.11 

"Platinum " . . 75.68 

Platinum, the heaviest body we know, is thus nearly a quarter of 
a million times heavier than an equal bulk of hydrogen, the lightest 
of known substances. 

50. We now proceed to connect bulk with weight, to find, not 
the absolute gravity of a substance, but its weight compared with 
another body of equal size, that is, its relative, or specific gravity. 
Any solid substance when immersed in water displaces a volume 
exactly equal to its own bulk, and, at the same time, loses a portion 
of its own weight just equal to that of the volume of water dis- 
placed. Water, found everywhere upon the globe, and easily puri- 
fied by distillation, is thus taken as the unit of comparison for 
solids and liquids. But variations of temperature alter the bulk of 
bodies, therefore sp. gr. is taken at the standard of 60°. 

51. Specific gravity of Solids. — Fill a vessel with water, 
Fig. 3. Fig. 3, and drop in it a piece of sulphur 

which has been weighed. A quantity of 
water will then escape into the dish be- 
low, equal in bulk to the sulphur. Weigh 
the escaped water in the lesser vessel. If 
the sulphur weighed two ounces, the 
water will weigh an ounce. That is, the 
sulphur weighs twice as much as an equal 
volume of water ; its specific gravity is, 
therefore, 2. The best plan, however, is to 
The solid displaces its bulk suspend the solid to the scale-pan of a bal- 
of water. ance by a fine thread, or hair, and then 

are given of the range of weights? What are the relations of platinum and hy- 
drogen? 50. What is specific gravity ? What is the principle upon which it de- 
pends ? 51. What is shown by Fig. 3 ? How is the* specific gravity of solids ob- 




HOW SPECIFIC GRAVITY IS OBTAINED. 



33 



Fig. 4. 




counterpoise it, or get its weight in the air. Immerse the sus- 
pended body in a vessel of distilled water, Fig. 4, and as it weighs 
less, remove weights enough 
from the opposite scale-pan to 
restore the last equipoise. Now 
divide the original weight in 
air by the loss in water, and 
the quotient is the specific grav- 
ity of the substance. For in- 
stance, a piece of lead weighs 
in air, 820 grains, and loses in 
water 71 grains. The weight 
in air divided by the loss in 
water, gives 11.5 as the specific SpnEna 

gravity of the lead. Weighing a substance in water. 

52. Specific gravity of Liquids and Gases. — Procure a small 
bottle and make a fine mark with a file and ink upon its neck. 
Counterpoise it in the balance. Fill to the mark with distilled 
wat^r at 60° and weigh it. Empty and fill again with the liquid, 
the specific gravity of which is required. Its weight, divided by 
that of the water, gives the desired result. Suppose the bottle 
holds a thousand grains of pure water ; it will be found to hold 
1,845 grains of sulphuric acid, which therefore has a sp. gr. of 
1.845. For 1000 : 1.000 : : 1845 : 1.845. It will hold 13,500 grs. 
of mercury, the sp. gr of which is hence 13.5 ; or Fig. 5. 
1,030 grs. of milk, sp. gr. 1.03. In practice it is 
usual to employ a bottle, Fig. 5, holding exactly 
100 or 1,000 grains of distilled water at 60°, which 
shows the result at once without calculation. The 
specific gravity of gases is obtained in a similar 
manner. A flask or globe suspended from the arm 
of a balance is weighed when empty, and again ( 
when filled with air. This gives the weight of 
air, which is taken as unity. Other gases are then Sp. Gr. Bottle, 
substituted for the air, and their comparative weights ascertained. 
Gases are subject to variations of density, not only by alterations 
of temperature, but by changes of atmospheric pressure; these 




tained ? 52. How is the specific gravity of liquids obtained ? of gases ? 63. How 

2* 



34 



CHEMICAL PHYSICS. 



weights are therefore taken at the standard barometric pressure 
of 30 inches. 

53. Specific gravity of Soil. — The specific gravity of soil, or 
any other substance in powder, is obtained as follows : Counter- 
poise a thousand-grain bottle and weigh into it 150 grs. of soil to 
be tested. Fill with water and weigh again ; water and soil give, 
say 1,096 grs., 150 of them are soil and 946 water; consequently 
54 grs. of water have been displaced by 150 grs. of soil. The cal- 
culation is then easy, 54 : 1.000 : : 150 : 2.777 sp. gr. of the soil. 
In practice a precaution is to be observed. The soil contains air 
among its particles, which would vitiate the result. To obviate 
this, fill the bottle but half full of water at first, and shake it well 
with the soil ; the air escapes, and the bottle may then be filled 
with water. 

54. Hydrometer.— Take a tumbler, or a light slender-necked 
bottle, loaded with some shot, and float it in pure rain-water ; it 
will sink to a certain depth, which may be accurately marked upon 
the glass. If now placed in brine or milk, the mark will stand 
above the surface ; the vessel not sinking so deeply as before, be- 

Fig. 6. cause the liquids are heavier. Place it in alcohol, 

and the mark will disappear below the surface ; it 
sinks deeper than at first, because the liquid is 
lighter than water. Instruments arranged on this 
principle, and called Hydrometers or Areometers, 
are used to measure the density of liquids. They 
usually consist of a glass stem, Fig. 6, terminating 
in a bulb below, loaded with shot or mercury, and 
floating in a narrow glass vessel, containing the 
liquid to be tested. Scales are fixed within the 
stem, zero being the point at which the instru- 
ment sinks in distilled water at 60°. In lighter 
liquids it sinks deeper, and the scale ascends from 
zero. In heavier liquids it floats higher, and the 
scale is reversed. These scales are arbitrary and 
different in the various instruments. Tables accompany them, 
so that we see at a glance the sp. gr. which corresponds to any 
number upon the scale. Instruments of this kind are much used 
by manufacturers and dealers, to determine the density or strength 
of liquors, syrups, oils, lyes, &c. 




Hydrometer. 



can we get t ^he specific gravity of soil ? 54. Describe the hydrometer. Why 



IMPOETAXCE OF SPECIFIC GRAVITY. 35 

55. Specific gravity is among the most important of the phys- 
ical properties of bodies. It affords an important means of identi- 
fying them. The mineral iron pyrites, for example, is in color 
almost exactly like gold, and is frequently mistaken for it. But 
they are at once distinguished by the difference in specific gravity, 
an equal bulk of gold being nearly four times heavier than pyrites. 
So if gold is debased by alloying it with a cheaper metal, the 
specific gravity promptly detects the fraud. The proportion of 
alcohol in spirituous mixtures, the richness of milk, the strength 
of various solutions employed in the arts, and the identity and pu- 
rity of many substances are determined with more or less accuracy 
by finding this property. 

§ IV. Minute Constitution of Matter. 

56. From the force which acts between masses at all distances, 
we now pass to the study of another class of forces which only 
come into play when bodies are in contact. They seem to pertain 
to the interior structure of substances, and hence before treating 
of them, it becomes important to inquire what that inner mechan- 
ism is, or how matter is constituted. 

57. Porosity of matter. — If we place a little water upon chalk 
or cloth, it disappears ; in a certain sense it penetrates them, but it 
does not enter the solid particles ; it only passes into vacant places 
termed pores. Not only loosely composed substances, as soil and 
flesh, but wood, rocks, stones, and even dense metals have the 
same porous texture. A pressure of a single atmosphere is sufficient 
to drive the liquid metal mercury through the pores of wood. 
Water gradually works its way through beds of rocks in the earth, 
and stones taken from the bottom of the sea at considerable depths, 
are found penetrated by it to their very centre. Mercury passes 
through lead, and water has been also forced through the pores of 
gold. So, that though matter is essentially impenetrable, it is also 
universally porous. 

58. Interior movements of bodies. — If a closed India-rubber 
bag filled with air be squeezed, it will be compressed into less 
bulk ; that is$ the particles of air will be forced nearer together. 

must its scales "be differently placed? 55. What are the uses of specific gravity? 
57. How extensive is the property of porosity ? 58. Describe the illustrations of 



36 



CHEMICAL PHYSICS. 




If alcohol and water be commingled, the 
mixture occupies a smaller space than did 
the separate liquids ; their particles have 
therefore approached closer to each other. 
If iron, or the densest of all metals, plati- 
num, be hammered, it will be driven into 
less compass, the metallic particles being 
forced into closer relation. A glass bulb 
with an open tu^e is partially filled with 
water, and inverted in a vessel of the same 
liquid, so that the upper space will enclose 
air, Fig. 7. If, now, heat be applied to the 
Expansion of a gas. ' ^^ fa Q a [ Y j s expanded and the water 
pressed down. If the bulb be filled with water up to a point marked 
upon the neck with ink, Fig. &, and the water heated, it will ex- 
Fig. 8. pand and rise above the mark. Or if a copper ball, 
which just slips through a ring, be heated, it is en- 
larged so that it rests upon the ring, and will not 
pass through it, Fig. 9. But if we remove the lamps 
and wait awhile, the heat gradually escapes ; the air 
shrinks to its former compass ; the water falls again 
to the ink-mark, and the ball drops through the ring. 
59. These expansions and contractions, exhibited 
by matter in its three-fold state> are the result of 
movements among the constituent particles, which 
first recede from each other 4 , and then come together 
again. Nor do these movements of the particles 
occur at random ; they are strictly regular. 
A definite increase of pressure upon sub- 
stances occasions a corresponding approach 
of their particles ; as heat is steadily applied, 
dilation steadily follows, and if they are sub- 
jected to cold, contraction occurs, the dis- 
tance between the particles diminishing with 
every degree of descending temperature. 

60. Atoms and their Interspaces. — From 
these facts r it is concluded that matter con- 
Expansion of a solid, sists of exceedingly minute particles which 




Expansion of a 
liquid. 

Fig. 9. 




the interior movements of bodies. 59. What is said of the regularity of these 
movements? 60. How is matter supposed to bo constituted? What are atoms? 



CONSTITUTION OF MATTES. 37 

are never in absolute contact, but are surrounded by unoccupied 
spaces, in which they are held by the action of internal forces. 
These ultimate, separated, material points, are called atoms, the 
word signifying an indivisible particle. Of their shape nothing is 
known. The intervals between them, it is supposed, are far greater 
than their diameters ; indeed the grouping of the celestial orbs is 
often taken to represent the distribution of atoms in a solid sub- 
stance. Sir Jonx Herschel asks why the atoms of a solid may not 
be imagined to be as thinly distributed through the space it occu- 
pies, as the stars that compose the nebula ; and compares a ray of 
light penetrating glass to a bird threading the mazes of a forest. 

61. For the sake of precision, it is convenient to restrict the 
term particles to those minute portions of bodies which are appre- 
ciable by the senses, or the microscope, while the word atoms des- 
ignates those infinitely smaller parts of matter of which we have 
no experience, being purely hypothetical creations. The term 
molecule is frequently used as the equivalent of atom, but it more 
properly signifies a cluster, or group of atoms, though still far 
more minute than sensible particles. The words pores and inter- 
stices are generally used as equivalent, but it would be well to 
confine the former term to those openings among particles which 
admit the passage of liquids, and limit the latter to those far smaller 
vacancies among ultimate atoms which are traversed by heat, light, 
and electricity. 

62. Divisibility of matter. — The division of matter may be 
carried to an amazing extent. Gold may be drawn out as a coating 
upon silver wire until the 492-thousand-millionth part of an ounce 
is still visible, with its proper metallic color and lustre. It has 
been estimated that in a drop of the blood of the musk-deer, such as 
would remain suspended upon the point of a fine needle, there are 
one hundred and twenty millions of globules. But these exam- 
ples of the divisibility of matter bring us only to the threshold of 
a world of wonders. Microscopic researches have introduced us 
to a realm of life peopled with animate beings, which are born, 
grow, reproduce their kind, and die ; and yet so minute, that many 
millions of them heaped together would not exceed in size a grain 
of sand. Eheexberg estimates that there were forty-one thousand 

How are they believed to be related to their interspaces ? 61 What are particles ? 
How do atoms differ from particles ? How is the term molecule used ? How are 
the terms pores and interstices used ? 62. What illustrations are given of the di- 



38 CHEMICAL PHYSICS. 

millions of their fossil shells in a single cubic inch of slate ; and yet 
these tiny beings are supposed to be endowed with organs of 
digestion, circulation, respiration, and locomotion- — these to be 
made up of complex organized parts — these of chemical elements, 
and these again of ultimate atoms ! 

63. The three states of matter. — Under the influence of various 
molecular forces, bodies assume the three-fold state of solids, 
liquids, and gases. In solids, the atoms are so rigidly held together 
by attraction that the body retains its figure. In the liquid state, 
attraction is so feeble that the particles slide over one another, and 
the body takes the flowing condition ; and in the gaseous or aeri- 
form state, the repulsive forces predominate, driving the particles 
asunder. Most substances are capable of being changed from one 
of these states to another, and some of them, as water and sulphur, 
take on all three conditions. The term vapor is applied to those 
gases which readily relapse into the solid or liquid form, as steam, 
vapor of iodine, &c. "V7e will now notice some of those forms of 
force which are exerted between bodies only when in contact, and 
which are known as molecular attractions. 

§ Y. Molecular Attractions. 

64. Cohesion. — Though the atoms of a solid are separated, yet 
it does not crumble to pieces. They are held together by a force 
which reaches across their interstices and binds them in a fixed re- 
lation. This force is the attraction of cohesion. It exists only be- 
tween particles of the same kind, and gives to bodies solidity and 
form. The hardness, elasticity, brittleness, malleability, and duc- 
tility of solids are the result of various unknown modifications of 
cohesive force. There is also a mutual attraction among the par- 
ticles of liquids. In a drop of liquid, cohesion attracts the particles 
into a rounded figure, against the influence of their weight, which 
would spread them out ; pendant drops still further exemplify the 
same force. 

65. Adhesion. — Adhesion is the force which unites dissimilar 
bodies and is exerted between substances of all kinds. The stick- 
ing of chalk to a blackboard, of metallic amalgams to the backs of 

visibility of matter? 63. What are the three states of matter? What is the con- 
dition of their atoms? 64. What holds the atoms of a soiid together? What 
properties of solids are due to cohesion ? What is said of the cohesion of liquids ? 



MOLECULAR ATTRACTIONS. 



39 




Fig. 11. 



looking-glasses, of glue to wood, and of mortar to bricks and 
stones, are familiar examples of adhesive force. 

66. Adhesion of liquids to solids. — If a glass rod be dipped 
in water, the liquid will rise round it above its level in the vessel, 
Fig. 10, and when withdrawn, it will be wet. fig. io. 

But if the same rod be dipped in mercury, 
there is an apparent repulsion, Fig. 11, and 
the rod when withdrawn is dry* If a rod of 
gold be dipped in the mercury it is wetted, or 
covered with a mercurial film. The wetting 
in this case shows an attraction between the 
liquid and the solid, and that it is sufficiently The glaS3 rod in water - 
strong to produce adhesion. But there may be attraction without 
wetting ; glass is not wet by mercury, and still they are attracted, 
as may be easily seen. Suspend a flat, circu- 
lar plate of glass to the arm of a balance, coun- 
terpoise it, and lower the plate, Fig. 12, over 
a cup of mercury. No matter how near the 
glass approaches, while there is no contact, 
there is no attraction. But as soon as they 
are made to touch, a slight adhesion occurs, — 
sufficient to lift a portion of the mercury above 
its level in the vessel, the amount of which 
may be exactly measured by the number of weights required to be 
placed in the opposite scale- 
pan to separate them. 

67. Conditions of Wet- 
ting. — If the adhesive force 
of any solid for any liquid ex- 
ceeds half the cohesive force 
of the liquid particles for each 
other, the solid will be wet. 
Thus, the adhesion of gold for 

mercury, and of water for Attraction of glass and mercury. 

wood exceeds half the cohesive force of the mercurial and watery 
particles for each other, consequently water wets wood, and mer- 
cury wets gold. But if the adhesion of the solid be less than half 




The glass rod in mer- 
cury. 



Fig. 12. 




65. What is adhesion ? 66. What is the effect if a glass rod be dipped into water ? 
Into mercury ? What, if a rod of gold be dipped into mercury ? What does the 
wetting show ? How may adhesion be shown to exist when there is no wetting ? 



40 



CHEMICAL PHYSICS. 



Fig. 13. 




Capillary tubes. 



Fig. 14. 



the cohesion of the liquid, wetting does not follow contact, as is 
exemplified by glass and mercury. 

68. Capillary Attraction. — If glass rods with small apertures, 
open at both ends, Fig. 13, be dipped in water, 
the liquid immediately rises through the orifices 
to a height which increases in proportion to 
the smallness of the openings. The same thing 
may also be beautifully exhibited by placing 
two plates of glass, Fig. 14, upon their edges in 
a dish of colored water, one end being joined, 
and the other slightly separated. The influ- 
ence of the gradually approaching sides of the 
glass in attracting the liquid upward is seen in 
the course of the curve. From the 
circumstance that this effect is best 
produced by tubes with very fine 
apertures, the attraction that causes 
these phenomena is called Capil- 
lary, (from capillus- a hair.) 

69. Reversed Capillarity. — If 
now a glass tube be dipped in mer- 

Riee of liquid between plates. -i . j. , , 

H F cury, we have again a disturbance 

of liquid equilibrium, but the effect is reversed. The interior 
column of mercury is depressed below the outside level, and its 
Fig. 15. surface exhibits a convex shape, as seen in Fig. 

15. The same thing occurs if the tube be greas- 
ed and plunged in water, and in all cases where 
the liquid cannot wet the solid. The common 
belief that depression in this case (as in that of 
the glass and mercury) is caused by repulsion, 
is quite erroneous. We have proved (29). that, 
instead of repulsion, there is a strong attraction 

between glass and mercury. The reversed cap- 
Convex liquid sur- .„ . ., « ,, , 

face. lllary action simply results from the preponder- 

ance of the cohesive over the adhesive force. In every body of 
fluid, each particle is kept in place by the mutual action of all the 
surrounding particles. But if a column of fluid be separated from 





67. When will wetting occur, and when not? 68. Describe Figures 13 and 14. 
What name has been given to this effect, and why ? 60. Explain Fig. 15. What is 



MOLECULAR ATTRACTIONS. 



41 




the surrounding mass by interposing the walls of a tube, the sides 
of which exert no equivalent adhesive force, the cohesion of the 
mass below draws down the upper and outer particles, and pro- 
duces a roundness or convexity at the top. 

70. Osmose. — Tie a piece of moistened bladder tightly over the 
end of a tube, place it in a vessel of water, and then fill it with 
alcohol up to the level. of the outer liquid. Fl0 16 

The fluid in the tube will shortly begin 
to ascend, and may rise to a considerable 
height, Fig. 16. The external water passes 
through the membrane and mixes with the 
alcohol, while, at the same time, a feeble 
current of alcohol flows the other way and 
commingles with the water. When differ- 
ent liquids are separated by a membrane in 
this manner, the one is transmitted fastest ° smose of liquids - 
which wets the barrier most perfectly. Duteochet, who first 
drew attention to this matter, named the inflowing current endos- 
mose, and the outflowing one exosmose; but these terms are lately 
less employed, and the phenomena are now known simply as 
osmose, from a Greek word signifying impulsion. The principle 
involved is a modification of capillary attraction. The pores of the 
bladder are short capillary tubes, into which water finds its way 
because it can wet the walls of the pore. Osmose is thus a result 
of the force of adhesion (66). 

71. Conditions of continuous Flow. — 
A capillary tube, however fine it may be, 
will not cause the liquid within it to over- 
flow; but if the liquid be removed from 
the top of the tube by evaporation or 
otherwise, the capillary force continues to 
supply it, and thus maintains the current. 
This may be seen in the wick of a lamp, 
when the oil is burned away and continu- 
ously supplied. If a small bladder be tied 
tightly to a tube, which is open at both 

° J * . , Osmose producing a con- 

ends and bent, as seen in tig. 17, the tinuous flow. 



Fig. 17. 




the cause of this? 70. Describe Fig. 16. What is osmose? Upon what does it 
probably depend ? 71. How may osmose be made to produce a continuous flow ? 



42 CHEMICAL PHYSICS. 

bladder and part of the tube being filled with alcohol and sub- 
merged in water, osmose will set in and the liquid rise and over- 
flow drop by drop into the cup, the motion continuing till the 
liquids are uniformly commingled. These principles probably 
afford an explanation of the flow of sap in plants, and the circula- 
tion of blood and nutritious juices in animals. 

72, Adhesion of gases to solids. — If iron filings are gently 
dusted over the surface of water, they float, though iron is eight 
times heavier than water. This is because of the adhesion and 
condensation of a layer of air upon their surface, which prevents 
the water from wetting them. The condensed air around the par- 
ticles forms a capillary cavity, and thus displaces a large volume 
of the liquid in comparison with that of the solid. Insects walk 
upon water and skim over its surface, because the air adhering to 
their feet forms capillary cavities, and prevents them from becom- 
ing wetted. 

73. Osmose of gases. — The adhesion of gases to solids gives 
rise to currents, which pass through porous bodies with consider- 

Fig. 18. aD ^ e power and velocity. Close the end of a glass 
tube with wet plaster. After it is dry, if the tube 
be filled with hydrogen, and its open end intro- 
duced into a vessel of water, the liquid rises rap- 
idly. The hydrogen escapes outward through the 
porous plaster, while at the same time air enters 
the tube from without. But nearly four volumes, 
of hydrogen escape for one of air which enters, 
and these are called the diffusion-volumes of hydro- 
gen and air. The diffusion volume of gases de- 
pends upon their density. If a thin sheet of In- 
dia-rubber be tied tightly over the mouth of a glass 
jar, and the vessel be then placed in an atmosphere 
Osmose of gases. f car DOn i c ac {^ movement slowly takes place ; a 
little of the internal air escaping outward, while so large a quantity 
of carbonic acid is transmitted inward as to distend the membrane 
into a dome-shaped cap, (Fig. 19.) If the situation of the gases be 
reversed, an opposite movement takes place, and the elastic sheet 
is deeply depressed, as the figure indicates. This principle is 

What natural phenomena probably depend upon osmose? 72. What examples 
are given of the adhesion of gases and solids ? 73. What does Fig. 18 6how ? 
What is meant by diffusion-volumes ? What is said of the osmotic action of in- 
dia-rubber sheets? Of the lung membranes ? 74. How do gases behave when ex- 




MOLECULAR ATTRACTIONS. 



43 



Fig. 19. 




Passage of gases through 
membranes. 



brought into play in atmospheric respiration. There is air on one 
side of the lung-membrane and blood on the other; oxygen is 
transmitted through the barrier from the air to the blood, and 
carbonic acid from the blood -to the air. 

74. Diffusion of gases.— The vapor of 
water will rise and fill a confined vessel of 
air just as if the space were a vacuum, ex- 
cept that it will take a little longer time. 
When gases are exposed to each other, 
they will intermix or diffuse uniformly, 
even in opposition to gravity. If two jars 
be connected by a narrow tube, (Fig. 20,) 
and the lower filled with carbonic acid, 
while the upper one is filled with hydro- 
gen, diffusion takes place through the nar- 
row passage. The light hydrogen descends, and the carbonic 
acid, though twenty times heavier, rises, and they become equally 
mingled in both jars. Our atmosphere owes its 
stability to this principle ; its constituents being 
perfectly intermingled. The baneful products 
of respiration, combustion, and decay, instead 
of accumulating, are incessantly dissolved away 
and dispersed in the atmospheric ocean. 

75. Adhesion of gases to liquids. — When a 
liquid is poured from one vessel to another, the 
gases of the air adhere to the descending stream, 
are carried downward, and a portion of them re- 
main combined with it. The force to be over- 
come by this adhesion is the elasticity of the gases, 
or the mutual repulsion of their particles. Press- 
ure and cold lower the elastic force, and therefore 
favor absorption. As the temperature rises, adhe- 
sion is diminished, and hence the readiest means 
of driving out a gas from solution is by boiling. Diffusion of ga~es. 

76. Diffusion of Liquids. — Adhesion takes place between the 
particles of dissimilar liquids, causing their intimate mixture : thus 
a drop of ink will spread, through a pint of water incorporating 
itself completely with the mass. This subject has been recently 




posed to each other ? Describe Fig. 20. How does this affect the atmosphere ? 75. 
What is the effect of adhesion among liquids? 76. Describe liquid diffusion. 




44 CHEMICAL PHYSICS. 

investigated by Prof. Graham. With suitable precautions to pre- 

Fig. 21. vent mechanical mixture, he placed small jars filled 

with liquids to be tested in larger ones containing 

distilled water as in fig. 21, and determined the 

amount of the inner solution that diffused into the 

water in a given time. Substances were found to 

differ greatly in diffusibility : chlorohydric acid is the 

most diffusible substance known. The equal diffusion 

Diffusion of °^ severa ^ solutions took place in the following times : 

liquids. Chlorohydric acid, 1; common salt, 2.33; sugar, 7; 

albumen, 49 ; caramel, 98. Substances thus tested are called dif- 

fusates. 

§YI. Solution. 

77. "Whenever the force of adhesion of the particles of a liquid 
for a solid exceeds the whole cohesive force of the latter, the solid 
is not only moistened, but its cohesion is overcome and solution 
occurs ; that is, the solid disappears — mixing uniformly with the 
liquid, which remains transparent. In this case the solid is said 
to have been dissolved by it, and the liquid employed is called the 
solvent. A liquid which dissolves one substance, may refuse to 
dissolve another, while substances insoluble in one liquid, are dis- 
solved in others ; and thus the hardest metals and minerals may 
be made to vanish and assume the transparent liquid form. 

78. Whatever weakens cohesion favors solution. Thus, by 
powdering a substance, cohesion is partially destroyed and the sur- 
face increased ; solution is consequently promoted. Heat, in most 
cases, contributes powerfully to solution, its effect being, as is sup- 
posed, to weaken cohesion, by increasing the distance between the 
particles of the solid ; yet there are marked exceptions. Water 
just above the freezing point dissolves twice as much lime as at 
the boiling point, while the solubility of common salt seems hard- 
ly affected by temperature. Some substances increase in solubility 
regularly as the temperature increases ; in many cases the solubil- 
ity increases faster than the temperature, and in others it rises 
with the increasing heat to a certain point, and then declines, 
while the temperature continues to ascend. 

77. What is solution ? Upon what does it depend ? What is a solvent ? 78. What 



SOLUTION. 



45 



Fig. 22. 



79. Saturation. — A liquid is said to be saturated when it has 
taken up as large a quantity of a solid as it can dissolve ; in which 
case the force of cohesion between the particles of the solid is 
equalled by the adhesion of the solid and liquid to each other. 
The solvent power of liquids varies much. Water is the great 
solvent, and so general and important is its use, that in speaking 
simply of the solubility of a body, it is always understood. 

80. Precipitation. — If the adhesive force of the solid and liquid 
can be overcome, cohesion takes place between the dissolved par- 
ticles, which again unite as a solid. This change is called precipi- 
tation, and the solid foraged, a precipitate. Precipitation may be 
effected in three ways : First, by removing the solvent, as in 
evaporation. Second, by modifying the solvent. For example, 
camphor dissolves in alcohol, but if water be add- 
ed, it unites with the alcohol and so changes it 
that it can no longer hold the camphor in solu- 
tion, which is precipitated as a white cloud, and 
afterward falls to the bottom of the vessel. Third, 
by adding a substance which combines with the 
dissolved body, forming an insoluble compound. 
Thus, if oxalic acid be added 
to lime water, it combines with 
the lime, precipitating it by the 
formation of an insoluble oxa- 
late of lime. This property is an 
important one in chemical opera- 
tions, as it enables us to separate Paper filters - 
the various constituents of a compound and de- 
tect the presence of a body when in solution with 
other substances. 

81. Filtration.— -The process of separating 
precipitates by straining or passing the fluid 
through any porous substance, is called filtration. 
The chemist uses unsized paper for this purpose, 
which permits the liquid to ooze slowly through, 
leaving the solid substance behind. The filter 
paper cut and folded as in Fig. 22 takes the shape 
of Fig. 23, which adapts it to the glass funnel. 




Fig. 23. 



Fig. 24. 




Fig. 25. 




Filter stand. 



is the relation of cohesion to solution ? Of heat ? 79. In what does saturation 
consist? SO. What is precipitation ? How may it bo effected f How is it impor- 



46 CHEMICAL PHYSICS. 

To prevent the adhesion of the paper to the sides of the glass, and 
thus facilitate the passage of the fluid, the filter is often plaited, 
Fig. 24. The funnel supporting the filter usually rests upon the 
stand, Fig. 25. 

82. Modes of Solution. — "Where there are mixed materials of 
variable solubility, with sufficient looseness of texture to permit a 
fluid to percolate through, one substance may be separated from 
the rest by being washed, or dissolved out. This is called lixivia- 
Hon, a term first applied to the extraction of ley from ashes 
(leaching). The soluble principles of plants are extracted by infu- 
sion, which consists in pouring upon the substance a hot liquid. 
Decoction consists in boiling for a considerable time the materials 
to be separated. Digestion is the slow and gentle action of a sol- 
vent with warmth; and maceration the act of softening the sub- 
stances by steeping. 

§YII. Crystallization. 

1. — PRODUCTION OF CRYSTALS. 

83. Crystalloid and Colloi<J states. — When the particles of 
many substances are loosened either by solution, melting, or other- 

Pig 26 w ^ se ? so as to be permitted freely to move, they tend 
* to arrange themselves in regular geometrical forms, 
/ \V termed crystals, of which Fig. 26 may be taken as an 
Vj3| example. All substances in which this tendency is 
j marked are called crystalloids. But all substances do 
j not crystallize, and the recent researches of Prof. Gka- 
~ffv ham, on the diffusion of liquids, have led him to conclude 
\ii/ that there is another general state of matter which is 
Crystal of definitely contrasted with the crystalloid, and which he 
quartz, terms the colloid, or glue-like. Water, acids> saline 
compounds, sugar, &c, are examples of crystalloids, while gum, 
albumen, jellies, and gelatinous silica- are colloids. The crystal- 
loids tend to assume hard, angular, unchangeable forms, while the 
colloids are of a soft gelatinous nature, very changeable, and char- 
acterized by rounded outlines. Crystalloid bodies predominate in 
the inorganic world ; colloid in the organic. The new views have 

tant ? 81. What is filtration ? How does the chemist effect it ? 82. What is 
lixiviation? Decoction? Digestion? Maceration? 83. What occurs when the 
particles of matter are loosened? What are crystalloids? Colloids? 84. Give 



CRYSTALLIZATION. 47 

much interest, and will be referred to again in organic chemistry. 
We here consider only the crystalline state. 

84. Crystals in Nature. — Nature teems with crystals. When 
it snows, the heavens shower them down (481), and ice is a mass 
of crystals, only so blended that we cannot distinguish them. 
Geology teaches that the materials of the globe were formerly in 
a melted state, so that in the slow process of cooling the opportu- 
nity was offered on the grandest scale for the formation of crys- 
tals. Hence, vast rocky systems have their constituents crystal- 
lized, and are known as the crystalline rocks. Metallic ores are 
nearly all crystallized, and immense regions of granite are but 
mountains of crystals. 

85. Crystals by Solution. — Crystals may also be artificially 
produced in various ways. The readiest method of obtaining 
them is to prepare a hot, saturated solution of some substance that 
will dissolve more freely at a high than at a low temperature, 
alum, for example, and suffer it to cool, when crystals will make 
their appearance. The liquid from which they are formed is 
called the mother liquor. Crystals are of all sizes, from the mi- 
nute particles of powder requiring a microscope to examine them, 
up to masses of crystallized quartz which are sometimes found 
weighing several hundred pounds. Artificial crystals are some- 
times produced five or six inches in length ; to obtain the largest 
and finest, the solution should be left quiet and inaccessible to dust. 

86. Vibration may so disturb the process as to FlG 2 7. 
check the growth of those which have commen- *. 
ced, and start a second crop upon them. Crystals / \\ 
are seldom found perfect, being generally irregu- / / \ \ 

lar, disguised, and distorted. Perfect alum crys- /- 7 ~~T\\ 

tals, for example, are regular octahedrons^ Fig. 27, \\L-_i ^ 

but Fig. 28 shows how they appear in the large \\ i / 
vat of the manufacturer. Sometimes the attrac- \j,/ 

tions are so balanced that a jar or agitation is ^ 

needed to start the action. In a perfectly still Crystal of a1 ^- 
atmosphere, water may be cooled & or 10 degrees below the freez- 
ing point without congealing, but the vibration of the vessel 
produces a sudden crystallization of part of the liquid into ice. 

examples of crystals in nature. Under what circumstances are they formed? 
85. What is the best mode of preparing them ? What is the mother liquor ? 
What of their size? Of their perfection ? Examples. 86. What is the influence 



48 CHEMICAL PHYSICS. 

* . Fig. 28. Any solid body intruded into the 

.gk liquid, by adhesion, may destroy the 

/ 3Er\, equilibrium and begin the play of 

zgglplfij the crystallizing attractions. Thus, 

/ggjlf. |^J% threads are stretched across vessels 

y0m^-- ik containing solutions of sugar, and 

4jjg ' ? form a nucleus around which rock 

m03t iHjplK |Kf 87 ' Cr Y stals b y Fusion.— Nearly 

^^^^^^ ^ ^ ^^^ ^^^^ all bodies when melted and cooled 

take the crystalline form, though this 

Masses of imperfect alum crystals. may not be at firgt per ceptible. The 

spaces left between the crystals which first form are completely 
filled up by the portions which solidify afterward, so that frac- 
ture reveals only a general crystalline structure, as may be 
observed in broken cast iron and zinc. Common sheet tin is 
beautifully crystallized, though nothing of the kind is apparent. 
If with weak acid we wash off the thin surface-film of metal, 
which had cooled too rapidly to crystallize, the structure will be 
Fig. 29. revealed of a beautiful, feathered appearance. 

To obtain crystals by fusion,, the excess of liquid 
must be removed from around those which are 
first formed. In this way beautiful sulphur 
crystals are produced. If a quantity of this sub- 
stance be melted, and then allowed to cool till 
a crust forms upon the surface and sides of the 
vessel, crystals will be formed within, which 
up urcrjsas. ma ^ ^ e geen e ^k er ^j breaking the vessel, 

Fig. 29, or by piercing the crust and draining off the interior 
liquid. 

88. By Sublimation and Decomposition.— Solid substances va- 
porized (sublimed) may be condensed in the crystalline form, as 
iodine, sulphur, arsenic. Camphor thus vaporizes and condenses 
in brilliant crystals upon the sides of apothecaries' jars by the rise 
and fall of common temperatures. It is also possible, by decom- 
posing a compound liquid or gas, to obtain one or more of its con- 
stituents crystallized. Various compound gases, when passed 

of agitation ? Of a solid introduced into the solution ? 87. What is said of crystal- 
lization hy fusion ? How are such crystals formed ? Examples. 88. Give exam- 
ples of crystals by sublimation. Decomposition. 89. What are the peculiarities of 




CRYSTALLIZATION. 49 

through red-hot tubes, deposit crystals. Metallic solutions are 
decomposed by passing a galvanic current through them — the 
metals being deposited in the crystalline form. 

89. Amorphism. — This term expresses the opposite of the crys- 
talline state. Amorphous bodies are without any regular form 
or trace of crystalline structure, as common glass, flint, wax, glue, 
wrought iron. They fracture irregularly, in any direction, and 
are generally more soluble, and less hard and dense, than in the 
crystalline form. Diamond is crystalline carbon ; charcoal and 
lampblack are amorphous carbon. 

90. Crystallization in the Solid state. — Whenever particles 
are left free, they arrange into systematic crystalline shape, and 
this strong propensity of matter is manifested even in solids. Thus 
sugar candy, at first transparent and amorphous, after some time 
becomes opaque and crystalline, Glass, by long-continued heat, 
though it does not melt, becomes also opaque and crystalline 
(Reaumur's porcelain). Brass and silver, when first cast, are 
tough and uncrystalline, but when repeatedly heated and cooled, 
they become brittle, and show traces of crystallization. Even the 
little liberty flie particles obtain by the motions of heating and 
cooling they improve to assume the crystalline condition. This 
is still better seen where the particles of bodies are thrown into 
motion by blows and vibration. Metals, by hammeriug, lose their 
ductility and tenacity and become brittle and crystalline. Copper- 
smiths, when hammering their vessels, frequently anneal them, to 
prevent their flying to pieces ; that is, they heat them, and then 
allow them to slowly cool. Thus also bells, long rung, change 
their tone ; cannon, after frequent firing, lose their strength, and 
are rejected; and so the perpetual jar and vibration of railroad 
axles and the shafts of machinery, gradually change the tough 
fibrous wrought iron into the crystalline state, weakening them 
and increasing their liability to fracture. 

91. Phenomena attending Crystallization. — This change of 
state is usually attended by change of bulk. Water in freezing 
expands to a considerable degree, and with great power; 1,000 
parts of water are dilated to 1,063 parts of ice; and the force ex- 
erted by the particles in changing positions is so enormous as to 
burst the strongest iron vessels. Heat is always manifested when 

amorphous bodies ? 90. How do solids become crystalline ? Under what circum- 
stances do copper, brass, and iron crystallize ? 91. How is water changed by crys- 
3 



50 CHEMICAL PHYSICS. 

crystals are formed, in proportion to the rapidity of the change 
from the liquid to the solid state. Light has also occasionally 
been noticed to accompany the process, but its cause is not ex- 
plained. Muddy and impure solutions often yield the largest 
crystals, and the presence of foreign bodies which do not them- 
selves crystallize, may thus modify the form which the crystal 
assumes. For example, common salt usually crystallizes in the 
form of a cube, Fig. 41, but if urine be present in the solution, it 
takes the form of the octahedron, Fig. 46. When a crystal is 
broken, there is a tendency to repair it ; it continues to increase in 
every direction, but the growth is most active upon the fractured 
.surface, so that the proper outline of the figure is restored in a 
few hours'. 

92. Purification by Crystallization. — When substances crys- 
tallize their tendency is to separate themselves -from any foreign 
bodies with which they may have mingled. For example, if com- 
mon salt and saltpetre be dissolved in water and the solution 
slowly evaporated, they will crystallize in different forms, and 
thus separate. Crystallization is hence a means of purification, 
and is of great importance in detecting adulteration mnd producing 
genuine articles, both for chemical and manufacturing purposes. 

2. -FORMS OF CRYSTALS. 

93. It is observed that in the living world curved lines and sur- 
faces prevail. Drops of liquid assume the spherical shape, as also 
do the planets. "We might, therefore, anticipate that dissolved 
substances, on being permitted freely to return to the solid state, 
would gather round a centre into spheres. Yet the shapes as- 
sumed under these circumstances are not curved, but angular, and 
are bounded on all sides by plane surfaces. This is well seen by 
comparing crystals with flowers, as in the ensuing figures. 

94. Symmetry in the plan of Nature. — In the production of 
her most perfect forms nature manifests a principle of symmetry — 
a similarity in opposite and corresponding parts. In the higher 
animals this principle is manifested in the double set of members 
right and left, while the organs of flowers and the parts of crys- 
tallization? What forces are manifested in crystallization? 92. How is crystalli- 
zation a means of purification ? 93. In what parts of nature do curved lines pre- 
vail ? What would this lead us to expect of crystals ? 94. What is symmetry ? 
How manifested in the higher animals? What kind of symmetry is shown 



CEYSTALLIZATION. 



51 



tals are also symmetrically distribut- 
ed. Fig. 30 represents the summit 
of a pyramid-shaped crystal, as we 
look down upon it. It consists of 
three portions exactly similar to one 
another. The faces, with their an- 
gles, are repeated in threes. The 
companion figure shows that the same 
kind of symmetry is found among 
flowers, as in the lily tribe. This is 
called three-member ed^ or triangular 
symmetry, and is very abundant in 
both the vegetable and mineral king- 
doms. Fig. 31 illustrates the four- 
membered, or tetragonal symmetry, 
which is abundant among minerals, 
but more rare among plants. The 
five-membered, or pentagonal symme- 
try, Fig. 32, is never found among 
perfect crystals, though it occurs 
abundantly in the animal and veg- 
etable worlds. Fig. 33 represents 
another kind of symmetry, in which 
the opposite ends are exactly similar 
to each other, and also the opposite 
sides. This is two-and-two-member- 
ed, or oblong symmetry. And finally, 
in Fig. 34, we have the case of simple, 
or bilateral symmetry, in which the 
two sides are exactly alike, as illus- 
trated in the higher animals. 

95. Axes of Crystals. — There is 
an almost endless diversity in the 
forms which substances take when 
crystallizing, but through all a per- 
vading plan has been discovered. The 
crystal is supposed to be traversed in 



Fig. 30. 




Three-numbered symmetry. 
Fig. 31. 




Four-membercd symmetry. 
Fig. 32. 



^ 



Five-membered symmetry. 
Fig. 33. 




ObloDg, or two-and-two-mern- 
bered symmetry. 

Fig. 34. 




Bilateral symmetry. 



in Fig. 30 ? What is said of the prevalence of three-membered symmetry ? Of 
four-membered ? Of five-membered? Describe oblong symmetry. What is bila- 
teral symmetry? "Where does the parallelism fail? In what cases is it most 



52 



CHEMICAL PHYSICS. 



Fig. 35. 







The regular system. 



Fig. 36. 




Square prismatic system. 
Fig. 37. 




Right prismatic system. 
Fig. 38. 




Oblique prismatic system. 
Ft^. 




Doubly oblique prismatic 
system. 



different directions by lines termed axes. 
These lines of symmetry govern the figure, 
and the same axes may be preserved, while 
the forms bnilt around them are endless. 

96. Six primary systems have been 
discovered, the axes of which are repre- 
sented by the large lines in the following 
figures. In each system they remain the 
same. The right-hand figures are seen to 
be derived ; from the left-hand by change 
of external form. 

97. The regular system, Fig. 35, has 
three equal axes at right angles to each 
otlier. Crystals of this system expand 
equally in all directions by heat, and 
refract light in the ordinary manner. 
Common salt and iron pyrites are exam- 
ples. 

98. The square prismatic system, Fig. 

36, has three axes all at right angles to 
each other, two of which are equal, while 
the third is of a different length. It ex- 
pands by heat equally in two directions 
only, and splits the ray of light passing 
through it .{double refraction), as do also 
the four systems remaining to be noticed 
(359). Examples : oxide of tin and cya- / 
nide of mercury. 

99. The right prismatic system, Fig. 

37, has three axes of unequal length, at 
right angles to each other. Crystals of 
this system expand unequally in the three 
directions of the axes. Nitre and topaz 
may be taken as examples. 

100. The oblique prismatic system has 



extensive? 95. What are the axes of crystals? What of their importance? 96. 
How many primary systems are there? How are they represented? 97. 
What is the arrangement of the axes of the regular system? 98. How are 
the axes disposed in the square prismatic system? How is it related to heat 
and light ? 99. Pescribe the right prismatic system. Mention examples of it. 



CRYSTALLIZATION. 



53 



Fio. 40. 



m 




Rhomb oh edral system. 

sulphate of copper and ni- 



three axes, which may be unequal, Fig. 38. 
Two are placed at right angles to each other, 
and the third is oblique to one and perpen- 
dicular to the other. Sulphate of soda and 
borax are common examples. 

101. The doubly oblique prismatic system 
has three axes, which may be all unequal 
and all oblique, Fig. 39. Examples : 
trate of bismuth. 

102. The rhombohedral system, Fig. 40, has four axes, three of 
which are equal in the same plane, and inclined at angles of 60% 
while the fourth is perpendicular to all. Examples : quartz, Ice- 
land spar, and ice. 

103. Cleavage.— If we apply the edge of a knife to a piece of 
mica, it may be cleft into thinner plates, and these may again be 
separated into the thinnest films. Nearly all crystals will thus 
separate in certain directions, disclosing polished surfaces, and 
showing the order of formation of successive parts. This me- 
chanical splitting of crystals is 
termed cleavage. Instruments for 
measuring the angles of crystals 
are called goniometers. 

104. Derivation of form. — The 
cube, Fig. 41, may be taken to 
illustrate change of figure, and 
this is chiefly effected by replacing 
edges and angles by\planes. The 
cube has eight edgesNand eight 
solid angles. If plane^surfaces 
are substituted for the edges, we 
get the secondary form, Fig. 42. 
If we replace the solid angles by 
planes, we have the form Fig. 43. 
If both these replacements occur 
together, the more complex Fig. 44 
results. If the edges of the cube 
be replaced until all traces of the 



Fig. 41. 



Fig. 42. 




Transformations of the cube. 



100. How does the oblique prismatic system differ from the preceding ? 101. How- 
are the axes arranged in the doubly oblique ¥ 102. In the rhombohedral ? Exam- 
ples. 103. What is cleavage ? 104. What example of the derivation of form is 



54 CHEMICAL PHYSICS. 

original planes disappeai, Fig. 45, the rhombic dodecahedron, is 
formed. And if the solid angles he replaced by planes to the 
same extent, we get Fig. 46, the regular octahedron. 

105. We have said that the secondary or derived forms of 
crystals are almost innumerable. Six hundred modifications of 
the six-sided prism have been enumerated by Dr. Scokesby, 
among snowflakes, while M. Bournon^ in a two-volume trea- 
tise, has delineated eight hundred different forms of the mineral 
calcite (carbonate of lime). Hatjx has described a single crystal 
which had 134 faces. 

106. The axes of crystals are not mere imaginary lines. The 
force which builds the crystal works unequally, and endows- it 
with different powers in different directions. In those crystals 
where the axes are all equal, light, heat, and electricity are con- 
ducted equally in every direction. But where the axes are un- 
equal, conduction of heat and electricity, hardness, elasticity, 
transparency, expansion by heat, and luminous refraction are cor- 
respondingly unequal, showing an actual difference of structure 
in the different directions ; just as wood varies in qualities when 
tested with or across the grain. This perfect regularity of struc- 
ture in crystals, by which they manifest different powers in dif- 
ferent directions, can only be explained by supposing that attrac- 
tion, in causing atoms to cohere in crystalline combination, does 
not act equally all around each atom, but between certain sides 
or parts of one atom and corresponding parts of another ; so that 
when allowed to unite according to their natural tendencies, they 
always assume a certain definite arrangement. This property of 
atoms is called polarity, because in these circumstances they seem 
to resemble magnets, which attract each other by their poles (159). 

107. Isomorphism. — Different substances may take the same 
crystalline form, and be substituted for each other, without chang- 
ing that form. Thus carbon, gold, and copper, among the ele- 
ments, and sulphide of lead, alum, and fluor spar, among the com- 
pounds, all crystallize in cubes or octahedrons which perfectly re- 
semble each other. This property is called isomorphism (equal- 
formed). Isomorphous bodies also ofteru closely resemble each 
other in chemical properties. ^ 

given ? 105. What is the extent of modifications ? What did Scoresbt ascertain ? 
M. Bournon? Haut? 106. What evidence is there that crystalline axes are real 



CHEMICAL ATTRACTION. 55 

108. Dimorphism.— It was formerly supposed that each sub- 
stance crystallized in one peculiar form, which afforded an unerr- 
ing clue to its identity ; but this is not invariably the case. Some 
substances crystallize in two different forms, and are called di- 
morphous (two-formed). Thus, sulphur deposited from solution 
takes one form, and another when cooled from melting. Nitre 
crystallizes in large quantities in one shape, and in small quan- 
tities it takes another. Some few substances crystallize in three 
distinct forms, and are called trimorphous. 



CHAPTEE II. 

CHEMICAL FORCES, LAWS, AND LANGUAGE. 

§ I. Chemical Attraction. 

109. We have seen the force of molecular attraction producing 
various interesting movements and changes, and at last overcom- 
ing the states of bodies so as to occasion that intimate combination 
of different kinds of matter called solution. But this attraction 
takes a still more powerful form, becoming so intense as altogether 
to destroy the properties of the substances engaged and give rise 
to new kinds of matter. The force which produces this class of 
effects is known as affinity or chemical attraction. Before con- 
sidering it, however, we will notice the nature of the substances 
upon which it acts. 

110. Elements and Compounds. — Modern chemistry has shown 
that there are about 64 elements, or different kinds of matter, which 
cannot, by any known process, be further separated or decomposed. 
Their names are given in the following table. Most of the ma- 
terial objects of nature are, however, compounds, formed by the 
union of these elements. Nature may thus be likened to a language, 
the elements to letters, and the compounds to words ; and as a 

thing3? 107. What is isomorphism ? 108. What is dimorphism? 109. What 
is the difference "between solution and chemical attraction? 110. What is 
a chemical element? How many are there? What are most material objects 
of nature? What are compound bodies? How may the constitution of 



56 



CHEMICAL PHYSICS. 



few letters, by their infinite diversity of combination, give rise to 
innumerable words, sentences, and books, so a few elements pro- 
duce all the boundless variety of natural objects. 

111. In the following list of elements, those which are rare 
and unimportant are printed in italics : 







Combining 






Combining 




ELEMENTS. 


Symbol 


number. 


ELEMENTS. 


Symbol. 


number. 




Aluminum, 


Al. 


13.70 


Niobium (Colum- 


Nb. 


48.80 




Antimony {Stibium), 


Sb. 


129.00 


bium) 








Arsenicum, 


As. 


75.00 


Nitrogen, 


N. 


14.00 




Barium, 


Ba. 


68.50 


Norium, 


No. 






Bismuth, 


Bi. 


210.30 


Osmium, 


Os. 


99.40 




Boron, 


Bo. 


10.90 


Oxygen, 


O. 


8.00 




Bromine, 


Br. 


80.00 


Palladium, 


Pd. 


53.20 




Cadmium^ 


Cd. 


56.00 


Phosphorus, 


P. 


31.00 




Cassiumj 
Calcium, 


Ce. 


123.40 


Platinum, 


Pt. 


98.60 




Ca. 


20.00 


Potassium (Kalium) 


K. 


39.00 




Carbon, 


C. 


6.00 


Rhodium, 


Ro. 


53.20 




Cerium, 


Ce. 


46.00 


Rubidium, 


Rb. 


85.36 




Chlorine, 


CI. 


35.50 


Ruthenium, 


Ru. 


52.11 




Chromium., 


Cr. 


26.30 


Selenium, 


Se. 


39.70 




Cobalt, 


Co. 


29.50 


Silicon, 


Si. 


14.00 




Copper (Cuprum), 


Cu. 


31.70 


Silver (Argentum), 


d ? - 


108.00 




Didymium, 


D. 


48.00 


Sodium (Natrium), 


Na. 


23.00 




Erbium, 


E. 




Strontium, 


Sr. 


43.80 




Fluorine, 


F. 


19.00 


Sulphur, 


S. 


16.00 




Glucinum, 


Gl. 


4.70 


Tantalum, 


Ta. 


68.80 




Gold (Aurum), 


Au. 


196.44 


Tellurium^ 


Te. 


64.50 




Hydrogen, 


H. 


1.00 


Terbium, 


Tb. 






Iodine, 


I. 


127.00 


Thallium, 


Tl. 






Iridium, 


Ir. 


98.60 


Thorinum, 


Th. 


59.50 




Iron (Ferrum), 


Fe. 


28.00 


Tin (Stannum) 


Sn. 


59.00 




Lanthanum, 


La. 


46.00 


Titanium, 


Ti. 


25.00 




Lead (Plumbum), 


Pb. 


103.60 


Tungsten (Wol- 


W. 


92.00 




Lithium, 


L. 


7.00 


fram), 








Magnesium,, 


Mg. 


12.16 


Uranium, 


IT. 


60.00 




Manganese^ 


Mn. 


27.48 


Vanadium, 


V. 


68.50 




Mercury (Hydrargy 1 


Hg. 


100.00 


Yttrium,- 


Y. 






rum), 






Zinc K 


Zn. 


32.60 




Molybdenum, 
Nickel, 


M. 


48.00 


Zirconium, 


Zr. 


22.40 




Ni. 


29.50 






I 


I 


112. Analysis 


and S 


ynthesis 


. — The separation 


of CO 


mponnc 


i 



bodies into simpler ones is called analysis. A compound may con- 
sist of compounds, and the first analysis may give only its nearest 
or proximate parts, while the second shows its ultimate constitu- 
ents, or elements. Thus flour may be decomposed into gluten, 
starch, oil, and water (proximate analysis) ; but these substances 
may again be resolved into their final elements (ultimate analy- 
sis). Qualitative analysis determines of what elements a com- 
pound consists ; quantitative analysis ascertains their proportions. 
Synthesis consists in combining the elements into compounds ; 
it is therefore the reverse of analysis. 

natural objects be compared to a language? 112. "What is analysis? Proxi- 
mate analysis ? Ultimate ? Qualitative ? Quantitative ? What is synthesis ? 



CHEMICAL ATTRACTION". 57 

113. Affinity. — The force brought into play in carrying on 
these changes is not manifested alike between all kinds of bodies ; 
some exert it only in a feeble degree, and others powerfully. It 
seems to manifest a kind of preference or election, which induced 
the alchemists long ago to name it affinity. The term, however, 
is unfortunate, as it properly signifies resemblance or relationship, 
whereas in chemistry it is only the name of the force which pro- 
duces chemical union. 

114. Conditions of its exercise. — Like adhesion, this force 
acts only between unlike bodies. If the earth consisted of 
but one kind of matter, mercury, for instance, there might be 
gravitation and cohesion, but affinity would be impossible. It 
might be physically changed by freezing, melting, or vaporizing, 
yet it would remain mercury still. Bat if sulphur were added, it 
would combine with the metal, forming a new substance, a com- 
pound, and thus chemistry, which implies a plurality of elements, 
would come into existence. 

115. However intimate the mixture of substances may be, 
their separate properties remain unchanged unless chemical action 
takes place. In the manufacture of gunpowder, its elements, char- 
coal, sulphur, and nitre, are separately reduced to a state of fine 
powder, then thoroughly mixed, moistened, and ground for hours 
with stones, and afterward intensely pressed and pulverized. But 
close as is the combination, it is only mechanical ; water will wash 
out the nitre, and bi-sulphide of carbon dissolve the sulphur, 
leaving the charcoal. The particles are not brought within each 
other's attractions, and affinity still slumbers. But a spark of fire 
awakens it, the elements rush into combination and disappear, 
leaving in their stead a huge volume of gaseous matter. 

116. Changes wrought by Affinity.— Newness of properties, 
either in color, odor, form, density, or some other quality, is a con- 
sequence of ail chemical union. It may convert two solids into a 
liquid, two liquids into a solid, or even two gases into a solid. 
Thus, when black charcoal and yellow sulphur combine, the com- 
pound formed is colorless as water, and highly volatile. Sulphur 
and quicksilver unite to form the bright-red vermilion. Nitrogen 

113. What is meant by affinity? Why is this use of the term unfortunate? 

114. How does the force of affinity differ from that of gravitation and*cohesion? 

115. How is the difference between combination and mixture illustrated ? 

116. What is said of the effect of affinity in changing the properties of bodies? 

3* 



58 CHEMICAL PHYSICS. 

and oxygen are neutral and tasteless, separate or mixed ; yet one 
of their compounds, laughing gas, is sweet, producing delirium 
when breathed ; and another, nitric acid, is an intensely sour, cor- 
rosive poison : they are both invisible, yet they form a cherry-red 
gas. Carbon and hydrogen are odorless, yet they combine to pro- 
duce our choicest perfumes. Mild and scentless hydrogen and ni- 
trogen form the pungent ammonia ; while suffocating and poison- 
ous chlorine, united with a brilliant metal, gives rise to common 
salt. The last-mentioned compound strikingly illustrates the enor- 
mous power of affinity in producing condensation. Thus 24 parts, 
by measure, of common salt contain 25.8 parts, or more than its 
own dullc, of the metal sodium, besides 30 parts by measure of 
liquid chlorine. No known , mechanical force could have pro- 
duced this condensation, and yet affinity readily effects it ;— the 
product, rock salt, being more transparent than glass. 

117. There is, however, a gradation in these effects. Sub- 
stances resembling each other are feebly attracted together, and 
only lose their properties partially ; and the wider the difference, 
the stronger is the affinity, and the more complete the transforma- 
tion. If the elements are very similar, the compound will show 
its parentage ; if quite unlike, all traces of its derivation will be 
lost. Thus, iron and mercury form a compound whose metallic 
aspect immediately betrays its origin ; but who, on looking at 
gypsum, would suppose it consisted of caustic lime and corrosive 
sulphuric acid. 

118. Affinities Unequal.— The chemical force which binds to- 
gether the constituents of a compound is definite, and, under like 
circumstances, remains always the same ; but it varies in intensity 
among different substances. Thus, carbonic acid will combine 
with soda, forming carbonate of soda. But if acetic acid be 
brought into contact with this compound, it will drive off the car- 
bonic acid and take its place, forming acetate of soda. Again, the 
affinity of chlorohydric acid for the soda is superior to that of the 
acetic acid ; it will therefore expel it and form a new substance. 
Tables have been constructed, representing the order of affinities 
among different substances, but so many causes disturb the play 
of this force that they are of but little value. 

Illustrations. 117. When will this change be greatest? When least? Exam- 
ples. 118. What is said of the variability of affinity ? What will be the effect if 
acetic acid be added to carbonato of soda? Hydrochloric acid to acetate of eoda? 



CHEMICAL ATTRACTION. 59 

119. Displacement. — Chemical compounds are formed in two 
ways. First, where the affinity is powerful, the substances com- 
bine directly when brought together. But by far the more fre- 
quent method, both in the laboratory and in nature, is where, in a 
body already formed, one of its ingredients is replaced by another 
substance, and a new compound results. The changes mentioned 
in the preceding paragraph are a series of displacements of this 
kind. This method of chemical action by substitution is very im- 
portant, and will be again referred to. 

120. Commencement of chemical action. — "When some sub- 
stances are brought into contact, chemical union instantly occurs ; 
but in most cases another force, heat, for example, is necessary to 
commence the action. Thus, a heap of charcoal may remain ex- 
posed to the air for years unchanged ; but, if heat be applied, it 
will arouse a chemical action between the charcoal and the oxygen 
of the air, which will continue till the entire mass is consumed. 
Phosphide of hydrogen, on the contrary, bursts into flame the 
moment it is exposed to the an\ 

121. Influence of Cohesion. — Cohesion obstructs the working 
of affinity. In very rare cases, as phosphorus and iodine, solids 
may directly combine ; but, as a general principle, cohesion must 
be entirely overcome, either by melting or dissolving one or both 
the ingredients, before chemical action can take place. Solution is, 
therefore, one of the grand processes of the laboratory, and sol- 
vents have been found for all substances. 

122. The nascent state. — The moment in which substances are 
liberated from union with each other is called the nascent (grow- 
ing) state, and, at this time, they often enter into combinations which 
could not be formed under other circumstances. Nitrogen and 
hydrogen gases, if mingled, do not unite ; but when set free at the 
same time, by the decomposition of vegetable matter, they readily 
combine to form ammonia. The chemical union of two substances 
is often effected by the bare presence of a third body, which re- 
mains unchanged during the process. This is termed catalysis, or 
contact action, and its causes are not understood. 



119. How does direct combination differ from combination by displacement ? 

120. How do substances differ in chemical energy? What force promotes it? 
Examples. 121. What effect has cohesion upon the play of affinity? Excep- 
tions. What is said of solution? 122. What is the nascent state! Its relation 



60 CHEMICAL PHYSICS. 

§11. Laws of Chemical Combination. 

123. The Mathematics of Chemistry.— "When instruments of 
weighing had attained a sufficient degree of perfection, it was 
found that, however often matter might change its form, nothing 
was either gained or lost — that its quantity remained the same. 
But other results of the highest importance also followed. It was 
discovered, that the force of affinity, as well as that of gravitation, 

' conforms to exact numerical laws ; that there is a mathematical 
order in the domain of chemistry as absolute as that which reigns 
in the realm of astronomy. As the forces which govern the heav- 
enly bodies cause them to complete their revolutions with infinite 
regularity and precision, so the chemical force which binds to- 
gether the constituents of a compound, produces its results always 
in the same definite and unalterable proportions. This is the 
foundation principle of the science. When the composition of a 
sample of water, common salt, or lime, is once accurately deter- 
mined, the knowledge applies to all water, common salt, and lime ; 
and so of every other substance. Pure water consists of 8 parts, 
by weight, of oxygen, combined with 1 part, by weight, of hydro- 
gen ; and we can produce it by the union of its elements in these 
proportions, and no other. So potash invariably consists of 39 
parts potassium and 8 oxygen ; and common salt, of 35 chlorine to 
23 sodium. Certain numbers, ascertained by experiment, and 
called combining numbers, express the proportions in which ele- 
ments invariably unite to form all chemical compounds. 

124. How marvellous is this order! The stones and soil be- 
neath our feet, and the ponderous mountains, are not mere con- 
fused masses of matter ; they are pervaded through their inner- 
most constitution by the harmony of numbers. The elements of 
the wood we burn are associated in fixed mathematical ratios. In 
the violence of combustion, the bond that held them together is 
destroyed ; they break away and rush into new combinations, but 
they cannot escape the law of numerical destiny. The burning 

to affinity ? Give an example. What is meant by catalysis ? 123. "What im- 
important discoveries followed the introduction of the balance into chemis- 
try ? What is said to be the foundation of the science ? Examples. What 
is the proportion of the elements in water ? In potash ? Common salt ? 
What are combining numbers ? 124. What is said of the constitution of all 



LAWS OP COMBINATION. 61 

candle gradually wastes away before us, dissolves in air, and 
passes beyond the reach of sight ; but in that invisible region, forces 
are playing among, its unseen particles with the same exactitude 
and harmony as among those which rule the constellations. And 
so is it with all chemical mutations. In the gradual growth of 
living structures, in the digestion of food, and in the slow decay 
of organic matter, no less than in its quick combustion, the trans- 
position of elements takes place in rigorous accordance with the 
laws of quantitative proportion. 

125. The Chemical Chart.— To represent these foundation facts 
of chemistry to the most impressible of the senses — the eye — 
and give the student the same advantage in the study of this 
science that is derived from maps in Geography and Astronomy, 
the author has prepared a Chemical Chart, which presents the laws 
of combination, in a great number of cases, in the simplest and 
clearest manner. The left column enumerates 15 of the most im- 
portant elementary substances, and represents each by a square 
colored diagram. Single squares represent elements, but when 
joined together, as shown by the converging lines, they indicate 
compounds. As a separate color is thus assigned to each element 
of a compound body, its exact composition is exhibited at a glance. 
The areas of the diagrams correspond to the combining numbers, 
and thus represent relative quantities to the eye. The hydrogen 
square being smallest, the oxygen square is 8 times larger, the 
carbon square 6, and the chlorine 85 times larger. Diagrams of 
the same color have always the same size. Thus oxygen, wher- 
ever found, is seen obeying the law of its fixed proportions ; its 
square is always of the same size, and so with all the other ele- 
ments.* 

126. Equivalents. — If we take equal quantities of two ele- 
ments, we do not find that they possess equal powers of attraction. 

* Chlorine, Carbon, Sulphur, and Phosphorus are represented upon the Chart 
by their natural colors. Fluorine, from its supposed-resemblance to oxygen in 
properties, has an analogous tint ; Nitrogen is of the color of the air (sky blue), -of 
which it is the chief ingredient. Oxygen, as the sustainer of combustion, and the 
agent which charges the blood from a purple to a florid tint, is represented of a 
crimson color. The bases of the alkalies have various shades of blue, correspond- 
ing to the strength of the alkalies which they form. (The alkalies restore the blue 
vegetable colors discharged by acids.) Aluminum, the basis of clay, is of a clay 
color. Silicon, which is said somewhat to resemble carbon, is of a dark color. 
Iron forms green-colored salts, and manganese those of a rose color. 

natural objects ? 125. Why was the chemical chart devised ? Describe it. 126. On 
what, is the idea of chemical equivalents based ? What example is given I 



62 CHEMICAL PHYSICS. 

There is as much chemical energy or neutralizing power in one 
grain of hydrogen as in 8 grains of oxygen ; and 35 grains of chlo- 
rine neutralize 8 grains of oxygen only equally well with 1 grain 
of hydrogen. Therefore, 1 gr. of hydrogen, 8 grs. of oxygen, and 
35 grs. of chlorine, are of equal value chemically — in other words, 
they are equivalents. When two bodies combine with a third, as 
they are each equivalents of the third bocly, so are they also 
equivalents of each other, and unite together in exactly the same 
proportions. For example, 1 part of hydrogen combines with 8 
of oxygen, and 35 of chlorine combine with 8 of oxygen, but 35 
of chlorine is the very quantity which combines with 1 of hydro- 
gen. Thus the proportion in which any two bodies combine with 
each other is that in which they combine with every other. 

127. Combining or equivalent numbers. — To each chemical 
substance, therefore, is attached its fixed number, and these num- 
bers are so mutually related, that no one can be changed without 
a corresponding alteration of the whole series. "We may employ 
any scale, so the relative values are maintained. We adapt the 
hydrogen scale, which is, perhaps, the best for general teaching. 
As hydrogen combines in the smallest proportion of any element, 
it is assumed as 1, oxygen will then be 8, nitrogen 14, &c. As 
oxygen, however, has the largest range of affinity, it is more con- 
venient, in laboratory work, to assume it as 100, in which case 
hydrogen becomes 12.5, and the other numbers are changed ac- 
cordingly. 

128. Multiple proportions. — When combinations occur in more 
proportions than one, the larger quantities are multiples of the 
smaller by a whole number. The compounds of nitrogen and 
oxygen furnish a beautiful illustration of this law. The propor- 
tion of nitrogen is the same in all : 14 parts of nitrogen to 8 of 
oxygen form a compound with one set of properties ; twice 8 of 
oxygen gives another compound with different properties ; thrice 
8 produces still a different substance ; 32 parts, another ; and 40, 
or- five times 8, yet another. (See Chemical Chart.) 

129. The law of equivalents applies to compounds as well as 
to elements. The equivalent of a compound body is the sum of 
the equivalents of its elements. Thus the equivalent of lime is 28, 

127. In fixing combining numbers, why is the hydrogen scale generally adopt- 
ed? "What are the advantages of the oxygen scale ? 128. What is meant by 
multiple proportions ? Example. 129. How does the law of equivalents affect 



LAWS OF COMBINATION. 63 

as it is a compound of calcium 20, and oxygen 8 (20 + 8=28) ; for 
carbonic acid 22; carbon 6, oxygen 16 (6+16=22) ; and of mar- 
ble or chalk, it is 50; lime 28, carbonic acid 22 (28+22=50). 
A knowledge of the combining numbers is of the first impor- 
tance in all departments of practical chemistry, whether in the 
laboratory, or in the manufactory, to determine the quantities in 
which materials shall be employed. The combining numbers of 
the substances upon the Chart should be committed to memory. 

1 30. Combination by Volume. — In dealing with gas, it is more 
convenient to measure than to w r eigh it ; and as it combines 
by equivalents in weight, it becomes important to know what 
amount of volume they occupy. When we take equivalent quanti- 
ties of the gases, we find that the spaces they fill do not bear the 
same relation to each other as the equivalent weights, nor are the 
spaces all alike, yet a very simple relation does subsist between 
them, which is shown as follows : The equivalent number being 
8 for oxygen, 8 grains of it are placed in a vessel winch will ex- 
actly contain them. The gas is then removed, and 32 grains of 
solid phosphorus introduced, that number being the equivalent 
of this element.. The phosphorus is then vaporized by heat, and 
the vapor exactly fills the vessel. The equivalent weights of oxy- 
gen and phosphorus are unequal,; but when brought into the 
same condition of vapor, they fill equal spaces, and have, therefore, 
equivalent volumes, which are expressed thus : oxygen = [j, 
phosphorus = Q. 

131. If, now, we take an equivalent of hydrogen, or 1 grain, 
we find that the vessel will hold but half of it ; its volume is 
therefore | | j , being double that of the oxygen or phosphorus. 
Consequently, if we wished to unite oxygen and hydrogen in 
equivalent weights, so as to form water, we would take one meas- 
ure of the former, and two of the latter. Sometimes gases are 
condensed by combination. Two measures of hydrogen and one 
of oxygen produce but two of watery vapor. Thus oxygen = Q], 
hydrogen = j I ], steam == [" 1 !• In measuring by volume, 
oxygen has hitherto been taken as the unit, but Geehaedt makes 
hydrogen the unit. His views will be better understood after 
studying the nomenclature. 

compound bodies? How are their equivalents determined? Example. Why 
is a knowledge of combining numbers important ? 130. How is the combining 
proportion of gases estimated ? How are combining volumes ascertained ? 



64 CHEMICAL PHYSICS. 

§ III. The Atomic Theory. 

1 32. The laws of chemical combination which have been ex- 
plained are independent of all speculation, being the result of 
facts established by multiplied observations and experiments, and 
may be verified at any time by accurately analyzing a few chemi- 
cal compounds. But this was unsatisfactory — an explanation was 
demanded — a reason was required for the remarkable behavior of 
chemical force in thus rigidly limiting the proportions of combin- 
ing quantities. To solve this problem, Dr. Dalton offered the 
Atomic Theory, which has already been referred to in its physical 
aspects. 

133. What it Teaches.— This theory assumes, first, that all 
matter is composed of indivisible, unchangeable atoms; second, 
that atoms of the same element have the same weight, but that in 
different elements they have different weights; third, that the 
combining numbers represent these relative weights ; and, fourth, 
that all chemical compounds are formed by the union of different 
atoms. 

134. This doctrine, if accepted, offers an explanation of the laws 
of combining proportions. Thus, if water be composed of an oxygen 
atom weighing 8, and a hydrogen atom weighing 1, then its com- 
position must be definite and invariable, and every specimen of it, 
whether it be a grain or a ton, must give, upon analysis, % of one 
gas and \ of the other. Also, if the atoms of each element possess 
invariable weight, they must, in all their combinations, exhibit 
equal and reciprocal values. And again, as an atom is the least 
quantity that can enter into combination, the compound can only 
be increased by the addition of whole atoms, so that the combining 
number expressing the large quantity must be an exact multiple 
of the single atomic number. The Chemical Chart offers a beauti- 
ful illustration of the atomic theory. 

135. Whether matter be infinitely divisible or not, is an old con- 
troversy, not yet settled. It would seem that it is so, as we cannot 
imagine a partijcle so minute that we may not conceive it to be 
again divided. But putting aside speculation as to what may oe, 
the chemist assumes that in the present order of nature there are 

131. How is it in the case of water ? 132. How have the laws of combination been 
determined ? Why was the atomic theory proposed ? 133. "What is its first as- 
sumption 1 Its second ? Third ? Fourth ? 134. What is said of this theory if ac- 



THE ATOMIC THEORY. 65 

ultimate indivisible atoms. The atomic theory has been objected 
to as not in accordance with all the facts of chemistry ; yet as a 
convenient hypothesis to facilitate study and inquiry, it has been, 
and is still of incalculable value. We subjoin two cases of its 
most recent application. 

136. Isomerism.—Until lately, it was the prevailing opinion 
that chemical properties depend solely upon chemical composition, 
and hence that similar composition necessitates similar proper- 
ties. For a long time, if two substances of different properties 
were found, upon analysis, to have one composition, it was held 
that the experimenter must have erred. But so constant and in- 
creasing were such results as at length to establish the fact that 
bodies of different composition may still have the same proper- 
ties. Bodies thus constituted are said to be isomeric, from isos, 
equal, and meros, measure, and are called isomerides. For ex- 
ample, the fragrant oil of roses and the chief illuminating con- 
stituent of common street gas are isomeric ; a compound atom of 
each consists of four atoms of carbon and four of hydrogen. To 
explain this we are compelled to assume that the constituent atoms 
of a compound may have different arrangements. The same atoms 
which if grouped in one way give rise to one substance, if re- 
grouped in another give rise to a different substance. 

137. If bodies have the same absolute composition, as in the 
above example, they are said to be metameric compounds, and the 
groupings of their constituent atoms may be represented by the 
structure of such words as ate, eat, tea, &c. But sometimes sub- 
stances have only the same proportioned composition ; they are 
then said to be polymeric compounds. Thus aldehyde consists of 
carbon, four; oxygen, four; and hydrogen, two; while acetic 
ether consists of just double these elements ; yet the per cent, pro- 
portion of both these compounds is the same. The relations of 
such bodies resemble those of the words Pa, Papa; Tar, Tartar. 

138. AUotropism. — Something analagous to this is manifested 
by the elements themselves*. Within the last few years it has 
been found that the elements may change their properties and 

cepted ? 135. What does the chemist assume concerning atoms? How is the 
atomic theory estimated ? 136. "What views have been held concerning the prop- 
erties and composition of bodies ? What has been recently discovered ? What is 
isomerism? Example? Explanation? 137. What is metamerism ? Polymerism? 
138. What is said of the different states of the same elements ? Example. What 



66 CHEMICAL PHYSICS. 

pass from state to state. We have a striking instance of this in 
carbon, which in one condition gives us the brilliant, transparent, 
and almost incombustible diamond ; in another, the black, opaque, 
easily inflammable charcoal ; while in another we have the metal- 
like graphite. This curious phenomenon is called allotropism, a 
word which means simply different states. It was at first sup- 
posed that but few of the elements were allotropic, but it is now 
found that nearly all of them take on this doubleness of condition, 
while some have several phases. The explanation of these effects 
is tha/t the atoms constituting the element are differently arranged 
in the different cases. 

§ IY. The Nomenclature — Chemical Language. 

139. The chemical nomenclature is a system of naming in 
which the structure of the terms employed expresses the composi- 
tion of the substances to which they are applied. The beautiful 
order of chemical composition is well fitted for such a device, and 
hence this nomenclature is the most perfect to be found in any of 
the sciences*. It was devised by a committee of the French Acade- 
my in 1787, as it was found that chemical compounds were multi- 
plying so rapidly that no memory could retain their arbitrary 
names. "With the progress of the science the principles of the 
nomenclature have been changed and extended. 

140. Naming the elements. — In the case of elements long 
known, the old established names were retained, but whe^e a new 
one was discovered, a name was given expressive of some leading 
quality by which it was distinguished. Thus chlorine takes its 
name from its greenish color ; iodine from its purple vapor ; phos- 
phorus (bearer of light) from its being luminous in the dark. The 
lately discovered metals are distinguished by the common termi- 
nation um, as platinum, thalium. Among non-metallic elements, 
analogy of properties is indicated by similarity of termination, as 
chlorine, bromine, fluorine ; or carbon, boron, silicon. 

141. Naming of binary compounds The union of two ele- 
ments forms a Unary compound (bis, twice), three elements form 

term is applied to it ? 139. What is the chemical nomenclature ? What is said of 
it ? When and by whom was it devised? For what reason ? What has changed 
it! 140. What rule has been observed in naming the elements? How are the 
metals distinguished ? How is analogy of properties indicated in other elements? 



THE NOMENCLATURE. 67 

a ternary, and four a quaternary compound. "Where the com- 
pound contains but one atom of each, both elements are designat- 
ed ?n the name. Thus a compound of oxygen and lead is called 
oxide of lead. When binary compounds are decomposed by the 
electrical battery, one element passes to the positive pole, and is 
termed the electro-negative element ; the other goes to the nega- 
tive pole, and is called the electropositive element. In forming a 
name, the electro-negative ingredient is placed first, and marks the 
genus, while the electro-positive comes last, and indicates the spe- 
cies. The first, or electro-negative element, is distinguished by 
the termination ide ; thus oxygen forms oxides; chlorine, chlo- 
rides; iodine, iodides; fluorine, fluorides; carbon, carbides; sul- 
phur, sulphides ; phosphorus, phosphides. The suffix uret was 
formerly applied in these cases, as sulphuret of lead, carburet of 
iron, but it is now less used. 

142. Acids. — Acids form an extensive and important group of 
binary compounds. They are generally soluble in water, sour to 
the taste, and change vegetable blue colors to red. Litmus, a 
blue vegetable extract, is commonly used as a test of acidity. 
"When not weakened by dilution with water, they decompose and 
destroy vegetable and animal substances, and likewise corrode and 
dissolve the metals. Acetic, sulphuric, and nitric acids are fa- 
miliar examples of this class. Acids are also distinguished by their 
powerful attraction for another class of bodies called oases. This 
is, indeed, their genuine test, for certain insoluble substances, as 
silica, neither taste sour nor affect blue paper, yet, when melted, 
they manifest acid properties, combining strongly with bases. 
The principle acids are of two kinds, called oxacids and liydracids. 
The former are so named because oxygen is their leading ingre- 
dient ; whereas, in the latter, it is hydrogen. 

143. Naming the acids.— Oxacids are named from the element 
with which the oxygen unites. Thus sulphur with oxygen gives 
sulphuric acid; carbon with oxygen gives carbonic acid. The 
varying proportions of oxygen are distinguished by terminations 
and prefixes. Thus, ic indicates the stronger, ous a weaker, and 

141. How is the number of elements in a compound denoted ? "When there is but 
one atom of each element in a binary compound, how is it named ? Which comes 
first? What termination has it? Examples. 142. What are acids? What is 
litmus? What is the distinguishing test of acidity? How are the principal acids 
divided ? 143. How are oxacids named ? How are the different proportions of 






68 CHEMICAL PHYSICS. 

the prefix hypo, which signifies under, a still weaker acid. Thus, 
nitric acid contains more oxygen than nitrous acid, and this more 
than hyponitrous acid. The prefix hyper means more, as hyper- 
chloric acid, or more commonly perchloric acid, which contains 
more oxygen than chloric acid. In naming the hydracids, both 
elements are mentioned ; as hydrogen and chlorine form hydro- 
chloric, or, according to the principle just laid down, chlorohydric 
acid ; iodine and hydrogen iodohydric acid. 

144. Bases. — All bodies which combine with acids and neu- 
tralize them are called bases. This class includes alkalies, alkaline 
earths, and many other substances wholly unlike them in char- 
acter. Alkalies, in their leading properties, are the reverse of acids. 
They have an acrid, nauseous taste, and restore the vegetable blue 
colors turned red by acids. Like acids, however, they are power- 
fully solvent and corrosive. Potash, soda, and ammonia are ex- 
amples. Alkaline earths, as lime and magnesia, possess these qual- 
ities in a lower degree. 

145. Naming the Bases. — Most of the bases are formed by the 
union of oxygen with metals, as oxide of iron, oxide of potassium. 
"When oxygen combines with the same element in different pro- 
portions, forming several oxides, the degree of oxidation is indi- 
cated by the use of prefixes. Thus, proto means one equivalent, 
or the lowest proportion of oxygen ; deuto, two ; and trito, three. 
Per denotes the highest degree of oxidation, and is often ap- 
plied to the deutoxide and tritoxide. ^'w-oxide is equivalent to 
deutoxide, and ^r-oxide to tritoxide, while sesqui-oxi&zs are those 
in which the oxygen is in the proportion of one and a half to one 
of the element with which it is combined. Some oxides of in- 
ferior basic properties are termed swft-oxides. 

146. Salts. — The combination of an acid and a base forms a salt. 
The properties of both constituents are neutralized, and the result- 
ant compound has entirely new qualities. The neutralization may 
be perfect or partial ; if perfect, a neutral salt is the result. If, 
however, there is not sufficient base completely to saturate the acid, 
an acid salt, or super-salt, is formed ; while, if the base is in ex- 
cess, a basic salt, or sub-salt, results. The term salt is not limited 

oxygen denoted? How are the hydracids named? 144. What are bases ? What 
are included in the class? What are alkalies? Alkaline earths? 145. How is 
the proportion of oxygen in a base expressed? 146. What are salts? Neutral 
salts ? Acid ? Basic ? What is said of the saline taste ? 147. How are the salts 



THE NOMENCLATURE. 69 

to bodies having a saline taste. Many tasteless substances, such 
as glass, marble, and various minerals and rocks, being composed 
of acids and bases, are properly salts. The constitution of salts 
will be noticed hereafter. 

- 147. Naming the Salts. — Salts are named from both their ele- 
ments, as phosphate of lime from phosphoric acid and lime. But 
as several acids of the same general name may combine with one 
base, the salts formed are distinguished by turning the ic of the 
acid into ate of the salt ; and ous of the acid into ite of the salt. 
Thus, nitric acid forms nitrates, phosphoric acid, phosphates, &c, 
while nitrous acid produces nitrites, and hyposulphurous acid, 
hyposulphites. The basic element of a salt is indicated by its 
usual prefixes ; thus, ^r^tesulphate of iron is sulphate of the 
protoxide of iron. Salts of the protoxide are called protossilts, 
and salts of the peroxide, perssilts. Illustrated exercises in the 
nomenclature of acids, bases, and salts, will be found upon the 
Chemical Chart. 

148. Symbols. — To facilitate chemical labor, Bekzelitts intro- 
duced a system of symbols, by which, not only the names of sub- 
stances, but their composition and changes are expressed by abbre- 
viations. The symbols of the elements are the first letters of their 
names, as, for carbon C, for oxygen 0, for hydrogen H, and for nitro- 
gen _T. But, as several substances may have the same initial letter, 
we either employ, to distinguish them, the first letter of their 
Latin names, or add a second small letter. Thus, as C stands for 
carbon, CI is taken for chlorine ; and as P represents phosphorus, 
we use, for potassium, K, from hzlium. the Latin for potash. A 
symbolic letter denotes, not merely an element, but one propor- 
tion, or atom, of that element. Thus, H stands for one equiva- 
lent of hydrogen, and O for one equivalent of oxygen. If more 
proportions than one are to be expressed, a small figure is added : 
thus, 2 stands for two proportions of oxygen, H 3 for three of 
hydrogen. In the table of elementary bodies (111) the symbol and 
combining number are given opposite each name. 

149. Formulae. — Tc express composition we place together the 
symbols of the elements of which the compound is formed; thus 

HO is the symbol for water, C0 2 for carbonic acid. Here the 

t _j 

named ? What does ate signify ? ite 7 Examples. How is the basic element indi- 
cated? 148. What are symbols? How are the symbols for the elements obtained? 
What does the symbol denote? How is more than one equivalent expressed? 



70 CHEMICAL PHYSICS. 

electro-positive element is placed first. A collection of symbols 
expressing composition or changes is called a formula. In ex- 
pressing changes the sign -f signifies addition to or mixture with, 
while the sign = signifies equivalency with or conversion into. 
The substances which act upon each other to produce chemical 
changes are called reagents, and the changes themselves reactions. 
The results of reaction are expressed by means of chemical equa- 
tions, in which the substances before the change are placed at the 
left, and the products of the change at the right. The reaction 
between nitrate of baryta and sulphate of potash is thus expressed : 

Sulph. of potash. Nit. of baryta. Sulph. of baryta. Nit. of potash. 

KO, SO^ + BaO, JSrcT 5 = BaO, S0 3 + KO, N0 6 

As nothing is either gained or destroyed in the operation, the 
quantities on each side are equal, as may be tested by forming an 
equation of the equivalent numbers. 

150. A bare statement of the elements of a compound, with no 
indication of the way in which they are combined, is called an em- 
pirical formula (28). Rational formulae express the views of the 
chemist as to the manner in which the elements are grouped. 
Thus the empirical formula for nitrate of potash would be KN0 6 . 
But as it is formed by the combination of nitric acid and potash, 
it is rationally written as if it consisted of them ; thus KO,N0 5 , 
the comma serving, as it were, to dissect the compound, and show 
how it is constituted. Sometimes the plus sign is used to indicate 
feeble attraction. Thus crystallized carbonate of soda is NaO, 
CO2 + IOHO, the ten equivalents of water being more loosely asso- 
ciated with the salt than the ingredients of the salt are with each 
other. To denote more than one equivalent of a compound, 
its formula is inclosed in a bracket with the number prefixed. 
Thus, three equivalents of nitrate of potash would be written 
3(KO,N0 5 ). The figure prefixed multiplies only the symbols in 
the brackets, as in the following formula for crystallized alum, 
which contains 3 equivalents of sulphuric acid : 

Al 2 3 3(S0 3 )+KO, S0 3 +24HO. 

149. What are formulas ? How are the symbols arranged ? What does + signify ? 
What is meant by the sign = ? What are reagents and reactions ? How are the 
results of reaction represented ? 150. What are empirical formulae ? Rational for- 
mulas? Give an illustration. What does the plus sign* sometimes denote? How 
is more than one equivalent of a compound expressed ? If brackets are omitted ? 



THE NOMENCLATURE. VI 

If brackets are omitted, the figures multiply all between them and 
the next comma or plus sign. 

151. Later views of Gerhardt and Laurent. — Certain ideas 
advanced by these chemists have been latterly growing in favor. 
Hydrogen, being the lightest substance known, is taken as the 
standard for the specific gravity of gases. It is found that the 
bulk or volume of a grain of hydrogen is the same as that of 14 
grs. of nitrogen, 35.5 grs. of chlorine, and 80 grs. of bromine. Xow 
these numbers are precisely the atomic weights of the bodies, so 
that the same numbers express both atomic weight and specific 
gravity. But the same bulk of oxygen weighs 16 grs., which is 
just twice its atomic number. And when the vapor volumes of 
carbon and sulphur are determined, it is found that to fill the 
same space takes 12 grs. of carbon and 32 of sulphur ; these 
again being just twice their atomic weights. To obtain uni- 
formity therefore, as well as for other reasons which cannot 
be here stated, the atomic numbers of oxygen,, carbon, and sul- 
phur are doubled. In this way the same numbers are made to 
express three facts, viz. : atomic weight, specific gravity, and 
combining volume. m 

152. On this view the symbols represetnt equal volumes of their 
elements. Hence the formula for chlorohydric acid, HC1, implies a 
combination of one volume of hydrogen with one of chlorine pT[ci| . 
Water is a combination of two volumes of hydrogen with one of 

oxygen, thus £Jo], and is written H 2 ; while ammonia, H 3 N, im- 
plies a union of three volumes of hydrogen with one of nitrogen " 



It will be noticed in the case of water that the doubling of oxygen 
is the consequence of halving the hydrogen; if we take equal vol- 
umes, their weights are as 16 to 1 ; but as there are two volumes 
of hydrogen, the composition of water becomes H 2 0, the oxygen 
being 16. There are other reasons for considering the composition 
of water as more complex than has been formerly supposed, so 
that without adopting the views of Gerhaedt, we may still regard 
water as H 2 2 instead of HO. 



151. "What place does hydrogen hold in the system of Gerhardt ? What relations 
have been fonnd to exist among some of the elements? Why are the numbers for 
carbon, sulphur, and oxygen doubled ? What is thus gained ? 152. On this view what 
do the symbols represent ? What does H C 1 imply ?How is water written ? Ammo- 



72 CHEMICAL PHYSICS. 

CHAPTEE III. 

ELECTRICITY. 

§1. General Considerations. 

153. The true idea of force is difficult to fix steadily in the 
mind; in the early stages of science it seemed impossible. (388) 
Forces were therefore materialized. It was said there are two 
kinds of matter, the gross sort which we can weigh, and the other 
which we cannot weigh — imponderable matter consisting of subtile 
fluids or particles which by their assumed properties produce the 
effect of force. Hence the forces heat, light, and electricity are 
known as imponderables. These crude conceptions of force may 
have been useful and necessary in the earlier progress of science, 
but they now no longer answer. The idea of a multiplicity of 
fluids of different natures is out of harmony with the whole body 
of recent facts, and has become a positive hindrance to the ad- 
vance of thought. All the tendencies of inquiry are toward a 
far closer relation than was formerly susjffccted between the dif- 
ferent modes of force— -a great and fruitful idea which might per- 
haps have been worked out earlier but for the notion that each 
force is a peculiar and distinct kind of matter. As we know nothing 
of force except through matter and by changes in it, the later views 
regard it as only an activity, or mode of motion, of common matter. 

154. We take up electricity before heat and light, because it is 
best adapted to familiarize the pupil with the general conception 
of polarity, which has become a fundamental idea in the newer 
philosophy of forces. For the same reason magnetism is the branch 
of electricity first considered. It is also desirable to study elec- 
tricity first, as it has furnished the most delicate and valuable in- 
struments for investigations in heat. 

155. Origin of the Science. — Nearly 2,500 years ago it was ob- 
served that when a piece of amber was rubbed, light substances 
near by became animated with motion, and flew toward it. This 
was considered marvellous, and amber was thought to have a soul. 

nia ? What is said in regard to water ? 153. Why were forces at first materialized ? 
How was matter divided ? What is said of this conception ? What is the present 
tendency ? 154. Why is electricity considered first ? 155. State its origin ? 156. 



MAGNETIC ELECTRICITY. 73 

Long afterward it was found that other substances manifested 
the same property ; they were, therefore, amber-like, and the pe- 
culiar agency received the name of electricity, from the Greek 
word electron, amber. 

156. Its present Importance. — For more than two thousand 
years nothing was done to unfold this principle, and yet the blank 
ignorance of that long period is perhaps less astonishing than the 
magical developments of the last century. Electricity has been 
demonstrated as the cause of the grandest phenomena of the at- 
mosphere, and the most extensive changes in the earth. It has 
given to chemistry new and powerful resources of analysis and 
synthesis ; it has added to its elements, multiplied its compounds, 
and revolutionized its theory. It has given to the physiologist a 
deeper insight into the forces of life, and to the physician a new 
method of combating disease. It copies pictures, moulds metals, 
separates ores, explodes the blasting charge in the earth and sea, 
and, as if to crown its brief and splendid career with a new en- 
dowment of civilization, it has literally broken down the barriers 
of space and time, and in the telegraph has conferred upon man 
an earthly omnipresence. 

157. It is now established that electricity is most intimately 
connected with heat, light, and the chemical and molecular forces. 
We can detect its presence, either as cause or effect, in almost 
every action and change around us ; and because of this close and 
varied relation to the other powers, as well as its essential interest, 
it deserves the earnest attention of the scientific student. 

§ II. Magnetic Electricity — Magnetism. 

158. The natural magnet is an iron ore which has the remark- 
able property of attracting to itself particles of iron or steel. If 
suspended, it takes a north and south direction, and from this 
pointing or leading property it is called the lead-stone, or loadstone. 
It derives its name magnet from the circumstance of its having 
been first discovered in the province of Magnesia in Asia Minor. 

159. Artificial Magnets. — If a steel bar be rubbed by a natural 

"What is said of its present importance ? 157. "Why should it be carefully studied ? 
158. What is the natural magnet ? "Whence are its names derived ? 159. Describe 
an artificial magnet? What are its poles? What is the mariner's com- 
pass? 160. How may the attraction and repulsion of magnetic poles be mani- 

4 



T4 



CHEMICAL PHYSICS. 




magnet, it acquires magnetic properties, 
and becomes an artificial magnet. If pro- 
perly shaped and poised upon a pivot, 
Eig. 47, it takes a northerly and southerly 
direction. The extremity which points 
northward is called the north pole of 
Magnetic needle. the magnet, and that which turns south- 

ward, the south pole. A magnetized steel needle properly sus- 
pended and attached to a card marked with the cardinal points, 
constitutes the mariner's compass. 

160. If a second needle be brought near the first, it will 
be noticed that they exert a powerful influence over each other. 
The north pole of each attracts the south pole of the other, 
while north pole repels north pole, and south pole repels south 
pole. In short, like poles repel, and unlike attract each other. 
These influences are exerted through all kinds of matter ; glass, 
wood, metals, or the human body. 

161. Distribution of the force.— The magnetic force is mani- 
fested chiefly at the poles, as may 
be seen by rolling a magnetic bar 
in iron filings; they accumulate 
mostly at the extremities, the cen- 
tral point being neutral, Fig. 48. If 



Fig. 48. 




Magnet in iron filings. 



a sheet of paper be laid upon the bar, and iron filings be dusted 



Fig. 49. 




Magnetic curves. 



over it, on gently tapping the 
paper, they gather thickly 
around the poles, extending 
away in curved lines, called 
magnetic curves, Fig. 49. Thus 
the two magnetic forces are al- 
ways produced simultaneously; 
are equal in amount, but op- 



posite in direction, and as these opposite powers are manifested 
in the poles of the magnet, they are called polar forces. 

162. Magnetic Induction.— The preceding experiments show 
that the magnet has the power of raising up magnetism in ad- 

fested? 161. What is shown by Fig. 48? How are magnetic curves pro- 
duced? What is shown by this experiment? 162. Explain what is meant by 
magnetic induction? How do Figs. 50 and 51 illustrate this? 163. What is 
the result of breaking a magnet? How do magnetized particles act? What 



MAGNETIC ELECTRICITY. 



75 



joining bodies ; — in fact, each of the little particles 
of iron becomes a magnet with a north and 
south pole. This may be proved by placing 
several bars of soft iron around the pole of a 
magnetic bar, Fig. 50, when they all become 
temporarily magnetic. The permanent magnet 
induces the influence in the adjacent bars, 
which are hence said to be magnetized by 
induction. A key may be supported by a magnet, 
Fig. 51, and this will hold a second smaller key, 
this a nail, and the nail a tack, the whole receiving 
its magnetism by induction from the bar, and each 
possessing its separate north and south polarity. 

163. Polarity of particles.— Now the particles 
of the magnet are in the same condition as the 
magnet itself. If a magnet is broken, as ^n Fig. 

Fl& - 52 - 52, and the pieces are 

IS Nj broken again and again, 



Fig. 50. 



Magnetic induction. 



Fig. 51. 



IS NHS Nl lS 



~N| the smallest particles still 
have opposite poles. But 




Magnetic chain. 



A broken magnet. 

as a magnet induces its own state in a piece of soft 
iron near it, so each particle induces a polar condi- 
tion in the adjoining particle ; that in the next, and 
thus the effect is propagated throughout the magnet. 
As each particle thus acquires polarity, and acts by induction upon 
all the others, the opposite powers become accumulated at the 
opposite extremities of the bar. This is Fig. 53. 

illustrated in Fig. 53, where the atoms 
are represented by circles, the shaded 
sides representing south polarity, and 
the unshaded their north polarity, 
while steel retains its magnetism- 



999(1 9999 
99(19(1(139 



Polaritj T of particles. 

It may be observed that 
-that is, its particles remain 
fixed in their polar relation, soft iron, on the contrary, only 
remains a magnet while immediately acted upon; its particles 
forced into the polar state by induction, resume their neutral rela- 
tion when the coercing power is withdrawn. 

164. The earth'is a vast magnet, varying in intensity at different 
times and places, which produces variations of the needle. A remark- 
is the effect ? What does Fig. 53 illustrate ? 164. What is the effect of the variation 
in the intensity of the earth's magnetism upon the needle ? What of the solar spots ? 



76 



CHEMICAL PHYSICS. 




Fig. 55. 




able correspondence has been observed between certain of these fluc- 
tuations and changes in the number and magnitude of the solar spots. 
Fig. 54. 165. The horse-shoe magnet. — Magnetic bars 

are usually bent in the shape of a horse-shoe, so 
that the poles are brought near together, as in Fig. 
54. They are then connected by a piece of iron 
called the armature, which adheres to the poles 
with a force depending upon the power of the 
magnet. In Fig. 55 we see the two poles of a 
horse-shoe magnet as if looking down upon them. 
Horse-shoe magnet. The space included within the circle is called the 
magnetic field ; the continuous line joining the 
poles represents its a$is, and the dotted line 
its equator. All substances which, when freely 
suspended between the poles of a magnet, ar- 
range themselves axially, are classed as mag- 
netic. They are but few, iron, nickel, cobalt, 
and oxygen being the most important. 

166. Diamagnetism. — Certain bodies, when 
suspended in the magnetic field, assume an equa- 
torial direction, as if repelled by the 
poles. The force thus manifested 
is so feeble that in experimenting, 
the objects are screened from cur- 
rents of air by a glass case, Fig. 56, 
in which o represents a bar of bis- 
muth suspended by fibres of unspun 
silk between the two poles of a mag- 
net. This property of bodies was 
lately discovered by Faraday, and 
named by him diamagnetism, while 
he terms common magnetism para- 
magnetism. Bismuth and antimony 
Diamagnetism. show it in the most marked degree, 

but it is also manifested by wood, leather, water, &c. ; in fact, all 
substances not magnetic are now regarded as diamagnetic. It was 
long thought that magnetism was a rare property, but it now ap- 
pears that all matter is affected, one way or another, by magnetism. 

165. What is the horse-shoe magnet ? Explain Fig. 55. When are substances said 
to he magnetic? 166. Do all bodies place themselves axially in the magnetio field ? 



Magnetic field. 

Fig. 56. 




FRANKLINIC ELECTRICITY. 



77 



Fig. 57, 




167. Oxygen is magnetic, but many other gases are diamag- 
netic. Faraday proved this in the following beautiful manner : 
A bent tube, Fig. 57, conveyed the gas 
for experiment into the centre of the 
magnetic field. Three short glass tubes 
open at both ends were suspended with 
their lower openings arranged in the 
equatorial line, with the middle tube 
just above the bent tube. So long as 
there is no magnetic action, the gas 

flows directly up the middle tube, but Diamagnetism of gases. 

the moment the magnet is brought into play, the diamagnetic gases 
were diverted into the side tubes. The course of the current was 
shown by placing a piece of paper moistened with ammonia in the 
lower tube, and other slips moistened with chlorohydric acid in the 
upper ones, the white fumes showing the direction of the current. 
Gases heavier than air flow downward, and for testing these 
the arrangement was reversed. A flame placed in the magnetic 
field is widened out equatorial! y. 

§ III. FranJclinic Electricity — Electro-Statics. 

168. The kind of electricity to be now noticed is called static 
electricity, from its being in a state of stagnation or rest.* It is also 
distinguished as FranTclinic electricity from Dr. Feaxklix, who was 
one of the most celebrated investigators of this branch of the science. 

169. Electrical excitation. — If a dry, warm glass tube be rub- 
bed with a silk handkerchief, several effects are produced by the 
friction. A feeble, crackling noise is heard ; there is a peculiar 
odor and a marked sensation when the tube is held near the hand 
or face, and if it be dark, faint, luminous flashes will appear to 
dart from the surface of the glass. If the tube be now presented 

* The word statics is derived from a Greek term signifying to stand, and is 
applied to forces in a state of rest or equilibrium. Thus hydrostatics treats of the 
pressure and properties of water in a state of rest ; and electrostatics of electricity 
m a stagnant or motionless condition. Dynamics, on the contrary, is derived from 
a Greek word signifying power, and indicates the science of matter in motion, or 
forces in action. Thus hydrodynamics considers the properties of falling or flowing 
water, and electrodynamics of electricity in a state of motion, as currents. 

What are Faraday's discoveries in this connection ? How may all bodies be classed ? 
167. How did Faraday determine the magnetic relations of gases? "What was the 
effect upon flame ? 168. What is static electricity ? Why is it also called Franklinic ? 
169. What are the effects of friction upon a dry, warm glass tube ? What are elec- 



IS 



CHEMICAL PHYSICS. 



to any light substances, as bits of paper or feathers, they are at- 
tracted to the glass. Bodies in which this quality has been aroused 
are said to be electrically excited or electrified, and are termed 
electrics. They are numerous, including all resinous, gummy, and 
glassy substances, hair, silk, dry gases, and air. 

170. Some bodies, as the metals, water, charcoal, &c, allow elec- 
tricity to pass readily through them, and are hence called conductors. 
Other substances, such as glass, resins, wool, do not readily allow its 
passage, and are termed non-conductors. As the latter tend to arrest 
or confine electricity, they are called insulators. Yet this simple 
division of bodies into conductors and non-conductors is hardly true 
to nature, for there is really no substance which perfectly conducts, 
or perfectly obstructs electricity. They differ only in degree. 

171. Electricity of the earth and air. — Our globe is a conduc- 
tor of electricity, and is termed the common reservoir. If an ex- 
cited body is connected with the earth by a conductor, the electri- 
city escapes into the ground. Air is a non-conductor ; and, per- 
vading all bodies, it acts as a universal insulator. All electrical 
manifestations^ around us depend upon this, for if air were a good 
conductor, no body could preserve its electricity. Yet moisture 
conducts, so that the air, when charged with dampness, carries off 
electricity quite rapidly. For successful experiments, therefore, 
the air should be dry. 

172. The Electrical machine consists of a glass cylinder or plate, 
Fig. 58, pressed by rubbers, and turned 
by a crank, so as conveniently to pro- 
duce a large amount of friction. Brass 
balls and rods are used to collect and 
carry away the electricity. The Ley den 
Jar is simply a glass jar covered inside 
and out with tinfoil as high as the line 
shown in Fig. 59. A metallic ball con- 
nects with the interior coating, the 
outer being in communication with the 
earth. If the ball is brought near the 
conductor of an electrical machine, it 
receives a succession of sparks, and be- 



Fig. 58. 




Electrical machine. 



tries? Mention some. 170. What are conductors ? Non-conductors? Insulators? 
Ib this division strictly true ? 171. What is the earth electrically? Is the air like 
the earth in this respect ? What if it were ? What is the effect of moisture ? 



FEAISTKLINIC ELECTRICITY. 



19 




comes charged. Then, on connecting the inner and outer coats by 
a conductor, discharge takes place, with a brilliant spark, and 
equilibrium is restored. The jar serves to accumulate F IG - 59.' 
electricity, and a connected series of such jars forms 
the Leyden Battery. 

173. Two kinds of electricity — If a ball made 
of pith of elder be suspended by a silken thread and 
brought near an excited glass tube, it will be first at- 
tracted to it, and then repelled from it. If another 
suspended pith ball be brought near a stick of excit- 
ed sealing wax, it will act in the same manner. Both 
balls are excited and both repelled. If the differently 
excited balls are now brought near each other, they Leyden jar. 
are attracted together, whereas if both had been excited by the 
glass alone or by the wax alone, they would have repelled each 
other. There are thus two kinds of electricity ; that from glass is 
called vitreous, and that from wax resinous. Each is self-repulsive, 
but bodies excited both ways attract each other ; or, as it is com- 
monly expressed, like electricities repel, and unlike attract — the 
same principle that we have just seen in magnetism. 

174. Electroscope. — The property of self-repulsion is employed 
to test the presence and intensity of electrical 
excitement. A simple electroscope is formed 
by suspending two pith balls by linen threads, 
as in Fig. 60. If touched by an excited 
body, they are repelled, Fig. 61, and the 
degree of divergence is a rough measure of 
the force awakened. 



Fig. 60. 



Fig. 61. 



175. On the same principle, slips of gold j^ 
leaf attached to a conducting rod in a glass ' ' 
jar, Fig. 62, form a very delicate electrom- pithTaiis. 




Excited 
pith balls. 



eter. Such is the sensibility of the instru- 
ment that a slight flap of a silk handkerchief on the plate at top 
renders the leaves divergent. "We thus become aware how trifling 
are the causes that disturb the electric equilibrium of the objects 
around us. "Not the smallest change in place or condition can 



172. What is the electrical machine ? Describe the Leyden jar. How is it charged 
and discharged ? "What is a Leyden battery ? 173. How may it be shown that 
there are two kinds of electricity ? What are they called ? How do they affect each, 
other ? 174. Explain the electroscope, Fig. 60. 175. What does Fig. 62 represent ? 



80 



CHEMICAL PHYSICS. 




Fig. 62. occur without interfering with this mysterious 

agency, although the balance is so quickly ad- 
justed that we are not aware of the disturb- 
ance. ' In cutting a slice of meat, there may 
pass between the steel knife and silver fork 
enough electricity to move the needle of a tel- 
egraph.' (O.Y. Walker.) 

176. Electric Tension. — The electrical ex- 
citement of a body may rise so high as to over- 
come the resistance which confines it and es- 
cape, rending a passage through the air, when 
Gold-leaf electroscope. a u excitement disappears. A body electrically 
excited is said to be charged ; the restoration of equilibrium is called 
discharge, and is seen in the electric spark and the flash of lightning. 
The degree of excitement or intensity of the charge is called elec- 
trical tension, and may be compared to the pressure of steam, or 
the bending of a bow or spring ; its discharge to their release. 

177. This analogy of the spring may be carried much farther. 

FlCK 63 « It is a principle of nature that forces 

develop themselves in a double or op- 
posite way. We see this in mechanics 
in the elasticity of a spiral spring, Fig. 
63. When unstretched it manifests no 
force. Nor can it be stretched from one 
end alone. If hooked to the pin P, and 
the weight W is attached, it will seem 
to be stretched by one end only. But 
this is a mistake; for by substitut- 
ing the weight Y for the pin P, the 
strain upon the spring is the same ; as 
the arrow indicates, the forces are double, 
equal, and opposite. 

178. The same principle is observed in electricity. It is a 
double force manifesting itself by actions and reactions which are 
equal and opposite. One kind of electricity cannot be produced 
unless it is accompanied by the other. Whenever vitreous elec- 
tricity is developed, a corresponding amount of resinous electricity 

Give instances of its sensibility. What does this show us ? 176. Explain what is 
meant by electric tension. To what may it be compared ? 177. In what manner 
are forces developed ? How may this be shown ? 178. How is it in electricity ? 




Duality and polarity of me- 
chanical forces. 



FRANKLES1C ELECTRICITY. 



81 



invariably accompanies it. It may not be at first perceptible, but 
will be recognized upon careful examination. Electricity is thus, 
like magnetism, a 'polar force. 

179. Electrical hypothesis. — Electricity has generally been re- 
garded as a subtile material fluid pervading all matter. Some hold 
that the two electricities are two fluids which are mutually at- 
tractive, though each is self-repellant. Feaskuh simplified the 
matter by regarding electricity as analogous to heat, and, as all the 
effects of heat and cold were explained by the excess or deficiency 
of a single fluid, caloric, he proposed to explain electrical effects 
by variations in quantity of a single electric fluid. He maintained 
that bodies vitreously electrified have an excess of it above their 
natural share, which excess he called the positive state, while bodies 
resinously electrified are deficient in the fluid, or in a negative 
condition. The positive electrical state he distinguished by the 
plus sign (+), and the negative by the minus sign ( — ). TVhen both 
are used together, they signify neutralization, or no excitement. 

180. The Franklinic terms and symbols are still used, but we 
must guard against their misguiding influence. Positive electri- 
city is no more positive, real, or powerful than negative, and the 
terms might be reversed so far as the character of the electricities 
is concerned. ZST or is the idea of a fluid at all adequate to explain 
the facts. Prof. Filler remarks: 'The 
supposition of an electric fluid is grad- 
ually being abandoned. The supposi- 
tion of a gravitative fluid might with 
nearly as much propriety be insisted 
on to explain the phenomena of gravi- 
tation, or a cohesive fluid to account 
for those of cohesion.' 

181. Electrical Induction. — Electri- 
cal bodies, like magnetic, act at a dis- 
tance to disturb the equilibrium of 
neighboring bodies. If an excited glass 
rod be brought near an electroscope, 
though there be no contact, the leaves 
will diverge, Fig. 64, and upon examination it will be found that the 

179. How has electricity been generally regarded? What was Franklin's explana- 
tion? What do the signs plus and minus signify? ISO. In the use of these terms 
what are we to guard against ? How is the conception of electricity as a fluid now 

4* 



Fig. 64. 




Induced electricity. 



82 CHEMICAL PHYSICS. 

cap is negatively electrified, and the leaves positively. The 
approach of the excited tube decomposes their natural elec- 
tricity, the negative element being attracted, and the positive 
repelled. This action of an excited body, without discharge, 
through a medium upon distant bodies, is known as electrical 
induction, 

182. Induction is a kind of preparation for discharge. "When 
electricity is about to move, or discharge to occur, the whole 
course through which it will pass is, as it were, felt out before- 
hand ; at first and infallibly the line of least resistance is found 
and pursued. If two conductors are before it, it takes the easiest 
course at the outset. 

Fig. 65. 133. Fig. 65 represents fragments of gold leaves 

^ casually laid upon paper, and producing with the 

'"''' paper a series of bad and good conductors. A dis- 

m/} cnar g e fi nc * s ^s path across the interrupted circuit 

Hj— j from P to N", burning up the leaves and parts of 

leaves, as shown by the shaded track. These re- 

H w markable results are necessary consequences of the 

'|\ principle of induction. The charged body induces 

l|k attractions in all directions, and the discharge will 

E''^ of course be determined through that range of ma- 

^ terials which from their nature and position are most 
excited ; which present the strongest attractions, and, 
of course, the least obstruction. 

184. Theory of Induction. — As there are all de- 
grees of conduction and insulation, Dr. Faraday 
Path oftbedig _* holds that we must look upon conduction and in- 
charge. duction as only different degrees of the same mode 
of movement ; in all cases, it is an effect communicated from atoms 
to atoms. If, when a body is electrified, its particles discharge in- 
stantaneously into each other, conduction is the consequence. If 
the particles do not readily discharge, but hinder the course of the 
electricity, they are immediately forced into positions of con- 
straint : they become polarized, and as each particle induces a 
state of polar tension in its neighbor, the effect is transferred to a 

regarded ? What is it thought to be ? 181. What is the effect of an excited glass 
tube brought near an electroscope ? What is induction said to be ? 182. When 
electricity is about to move, what course does it take ? 183. Explain Fig. 65. Why- 
is this? 184. Describe Faraday's theory of induction. Explain Fig. 66. On 




VOLTAIC ELECTRICITY. 



83 



Fig. 66. 



© 9 © a 
© © © b 
© © © £ 

© q ©^ 


Q 


Polarization 
of atoms. 



distance. In Fig. 66, P represents a positively charged 
body, and abed intermediate particles of air. These 
are thrown into opposite states or polarized, as is rep- 
resented by the white and black sides of the spheres, 
and thus the effect is propagated to the body N, which 
is electrically excited. We have said that insulators 
arrest electricity, but on this view they only stop move- 
ment by conduction ; they transmit it by induction 
through the polarization of their particles. As the polar 
particles are in active relations of force to those around, 
it is obvious the effects may be propagated in various 
directions. Hence the polarization may occur in curved 
lines, and induction take place round corners and behind obstacles. 
185. Sources of electricity. — These are various. Besides or- 
dinary friction, the rubbing of water particles against the aperture 
when steam escapes is a powerful source of electricity. When- 
ever bodies are pressed together and separated, they exhibit traces 
of opposite electrical excitement. Many crystals are made elec- 
tric by mere compression ; Iceland spar pressed between the fingers 
becomes excited. If tourmaline be 
slowly heated, it becomes power- 
fully excited, as is represented in 
Fig. 67 O t o. 1). When the heat is 
no longer added, the excitement dis- 
appears, but, as it cools, the electri- 
cal conditions are reversed (No. 2). 
That the particles are polarized through the whole length is 
shown by the fact that if the crystal be broken, as the tempera- 
ture falls each piece is electrified (No. 3). Fracture, crushing, 
and combustion, all produce electricity. Carbon in burning is neg- 
ative, while the carbonic acid formed is positive. 



Fig. 67. 




+ - 

Tourmaline electrified by heat. 



§ IV. Voltaic Electricity — Electro- Dynamics. 
186. We have now to consider electricity in a state of motion 
and active force. This important branch of the science was dis- 
covered about 1790, by Galvaxi, while working with some dis- 
sected frogs, and in his honor is frequently called Galvanism ; but 

this view what is insulation ? 1S5. "What other sources of electricity are men- 
tioned? What does Fig. 67 represent? 1S6. What is electro-dynamics? Who 



84 



CHEMICAL PHTSICS. 



its most illustrious cultivator was Volta, whose name is insepara- 
bly connected with its foundation and progress, and from whom 
it is also called Voltaic electricity. Both these celebrated men 
were Italians. 

187. Sulzer's experiment. — It was noticed by Sulzer, about a 
hundred years ago, that, if a silver coin be placed upon the tongue, 
and a piece of zinc beneath, a peculiar tingling sensation or taste 
will be perceived when the ends of the metals are made to touch ; 
or, if the silver be pressed between the upper lip and the teeth, a 
flash of light will be observed when the metallic contact is made. 
This is an effect of voltaic electricity. 

188. We have just stated that electrical disturbance may arise 
from simple contact of different substances. Volta supposed that 
these effects were due to the same cause. But it is now generally 
considered that when electricity arises by metallic contact, it is 
owing to chemical change. Voltaic electricity is produced when 
two unlike solids, usually metals, are immersed in a liquid which 
dissolves only one of them. It is a general law that no chemical 
action occurs unaccompanied by electrical disturbance, although 
the quantity is often so minute as to escape detection. 

189. The Voltaic Circuit. — A strip of zino 
and one of copper are placed in a vessel 
containing water, to which has been added 
a little sulphuric acid. If not permitted to 
touch each other, as in Fig. 68, there is no 
effect. But if brought into contact, as seen 
in Fig. 69, several results ensue. The acid in 
the water grows weaker ; the zinc strip is cor- 
roded, wastes away, and bubbles of gas are 
seen to escape from the surface of the copper. 
If the metals are separated, the action ceases ; 
and, if this is done in the dark, a minute 
spark will be seen. Electricity seems to flow 
round and round in the direction of the ar- 
rows, like an invisible stream. The com- 
bination through which it passes is termed a 
voltaic circuit, and the circulating force an 
electric, or electromotive current. If the plates 



Fig. 68. 




No effect. 




The voltaic circuit. 



discovered it? Why is it called voltaic electricity? 187. What was Sulzer's 
experiment ? 188. When is voltaic electricity produced ? What is said of chemical 



VOLTAIC ELECTRICITY. 85 

be connected by means of a wire, which may be a few inches or 
many miles in length, a current passes through the whole distance. 
If a non-conductor be substituted for the wire, the action instantly 

ceases. 

190. The source of the electricity is the decomposition of the 
water, its oxygen combining with the zinc to form oxide of zinc, 
while hydrogen gas is set free. But the oxide of zinc is insoluble, 
and would form an impervious coating upon the plate, and quickly 
stop the process. This is prevented by the sulphuric acid which 
unites with the oxide, forming sulphate of zinc, and thus the plate 
is kept clean and the action maintained till the metal is consumed, 
or the acid all neutralized. 

191. Amalgamation. — A slip of pure zinc introduced into the 
acid is but slightly, if at all, acted upon. But commercial zinc is 
contaminated with lead and other metals, the effect being to create 
minute currents between them and the adjacent particles of zinc, 
thus corroding the plate and wasting the electric force. To pre- 
vent this, the clean zinc surface is rubbed over with a little mer- 
cury, which forms an amalgam with it, increasing the energy of 
the zinc, and enabling it to be kept in acid without corrosion. 

192. Electrodes. — To the plates are usually soldered wires 
with terminals of platinum to withstand the action of corrosive 
liquids. The ends of these wires are known as the poles of the 
circuit, from an idea that they exerted an attractive and repellant 
action, like the poles of a magnet. But Faraday has proved that 
there is no attraction or repulsion in the case, and suggested the 
better term electrodes, which means simply a door or way for the 
electricity. 

193. Positive and negative parts of the circuit. — The terms 
positive and negative have a double application to different parts 
of the circuit, which often confuses the student. The copper pole 
is positive (which may be easily remembered by associating the 
four p's of the three words), and the zinc pole negative. But 
these terms are reversed when applied to the plates — zinc being 
now positive and copper negative. Whatever be the metals used, 

action? 189. Describe the voltaic circuit ? Its effects? 190. "What is the source 
of the electricity ? What is the office of the sulphuric acid ? 191. What difficulty- 
arises in the use of common zinc? How remedied? 192. What are the poles of 
the cirouit ? Why is ' electrodes 1 the better term ? 193. How are the terms positive 
and negative applied? Where does the positive electricity originate, and what is 



86 



CHEMICAL PHYSICS. 




the positive plate, or the one chemically acted upon, originates 
positive electricity, which passes over to the negatively affected 
plate, and is by that delivered at the positive electrode. 

194. Polarities of the circuit.— The electric current originates 
in chemical changes, and requires a compound liquid capable of de- 
composition by one of the metals. To bring the chemical force 
into play, the voltaic circuit must be arranged so as to form a 
continuous chain of polarities. The theory of the action may be 
illustrated by representing the atoms of the liquid to the eye. A 

FlG T0# plate of zinc with one end in chlo- 

rohydric acid assumes a state of 
electrical tension, and induces the 
same state in the atoms of hydrogen 
and chlorine which compose the 
acid, Fig. 70. The positive zinc at- 
tracts the adjacent atom of negative 
Polarity, but no current. chlorine, but not with sufficient 

force to take it from the positive hydrogen. Nor is the matter 
helped by completing the circuit with another zinc plate, as shown 
in the figure. At two points, above and below, like electricities 
repel each other; the tensions are balanced, and there is no 
motion. 

195. But if now the second zinc plate be replaced by one 
of copper, the conditions are altogether changed; the polar- 
ities are unlocked, the liquid is decomposed, and there is an 
active circuit, as illustrated in Fig. 71. The copper imparts an 
additional amount of positive electricity to the zinc, the ten- 
sion of which is thus heightened, and receives a portion of ne- 

A powerful polar influence is thus 
communicated to the liquid. The 
increased attraction of the zinc 
causes it to decompose the adjoin- 
ing atom of acid, combining with 
the negative chlorine ; while the 
atom of hydrogen, powerfully po- 
larized by induction, acts in the 
same way, decomposing the next 



gative electricity in return. 
Fig. 71. 




Conditions of circulation. 



its course ? 194. In what does the electric current originate ? "What does it re- 
quire ? "What is the effect of one zinc plate in the acid ? Of two ? 195. What is 
the effect of replacing the zinc by a copper plate ? Draw Figures 70 and 71 upon 




VOLTAIC ELECTRICITY. 87 

atom of acid, uniting with its chlorine, and forming a new com- 
pound atom. This is repeated through the series, and the last 
atom of hydrogen, having its positive electricity neutralized by 
the strongly negative copper, is set free. 

196. Currents. — Here again we are in danger of being misled by 
terms which involve material views of force. The word ' current ' 
is to be used in a sense entirely figurative. In dealing with sub- 
tile, invisible forces, it is easiest to view them through the medium 
of analogy and apply terms borrowed from sensible objects, The 
effects of electricity resemble those of a stream, and from ap- 
propriating the terms we gradually acquire the idea of an unseen 
but real fluid flowing in currents through substances, or from one 
to another. But all we know in the matter is progressive effects, 
and all we are entitled to assume is the progress of force. The 
movement of electricity is more analogous to that of sound, where 
pure impulse and not matter is borne forward. (319) If the ivory 
ball at one extremity of a closely sus- Fig. 72. 

pended series, Fig. 72, be raised and 
let fall, the one at the other end will 
be struck off, the intervening balls re- 
maining in their places, yet trans- 
mitting the impulse; there is only a Elastic bails. 
progress of force. "While the term current in electricity is con- 
venient and perhaps indispensable, we mean by it the same as if 
we should speak of a current of sound, or, in the case of the ball, 
a current of motion. 

197. Two Opposite Currents. — "We have seen that elec- 
tricity, like magnetism, is a polar force, displaying itself 
in a twofold way. "When produced in the voltaic circuit, it 
separates into two equal and opposite powers — two currents 
which, when they meet, instead of doubling, neutralize each 
other. The electricity thus produced has been likened to a 
double-headed arrow rapidly elongating itself in opposite direc- 
tions. At first they move from each other, but turning through 
equal semicircles, they meet, each arrow-head destroying the other. 



the blackboard, and explain them. 196. In what danger are we from using the 
word current? What do we really know in the matter? To what is the move- 
ment of electricity analogous ? To what else is it compared ? 197. In what respect 
have we seen electricity to be like magnetism ? To what are the movements of the 
current likened ? What is meant when the direction of the current is spoken of? 



88 



CHEMICAL PHYSICS. 




The two currents. 



Fig. 73. The two opposite electricities Or polarities con- 

stantly meet and neutralize each other, and are 
constantly renewed. To avoid confusion, when 
the direction of the current is spoken of, the 
positive alone is indicated. In Fig. 73 the 
dark arrows show the direction of the positive 
current, the dotted arrows that of the nega- 
tive. 

198. The Voltaic Pile.— The power of the 
circuit may be increased by repeating its elements. The pile dis- 
covered by Volta and named after him was the first contrivance 
for augmenting the force of ; the electric current. It is made by 
preparing small plates or diftfs of metal, usually copper and zinc, 
and placing between them pieces of flannel moistened with an 
acid or saline solution. Such a pile is represented in Fig. 74. The 
Fig. 74. cloth is placed between the metals, and the order 
begun is preserved. Commencing at the bottom 
there is copper (c), flannel (f), zinc (z), and upon that 
copper, flannel, zinc, and so on to fifty or a hundred 
sets, as may be desired, 74. The lower or copper 
P)>C end is positive, and the other negative ; a current 
therefore moves in the direction of the arrows. 
This form of instrument gives a strong effect at first, 
but rapidly declines in power. 

199. The Galvanic Battery.— -To augment the 
electrical effect, and at the same time secure steadi- 
ness of action and convenience of management, the 
compound circuits are arranged in other forms known as voltaic 
or galvanic batteries. A series of cups or cells, containing an 

acidulated liquid, are arranged, in 
each of which there is a plate of 
copper and another of zinc; the 
copper plate of one cup being con- 
nected by a copper wire with the 
zinc plate of the preceding cup, 

Voltaic battery. Fio\ 75. 

200. Smee's Battery.— We have already noticed the tendency 

198. How may the force of the circuit be increased ? What is the voltaic pile ? 
Explain Fig. 74. 199. What objects are secured by the galvanic battery ? How is 
it made ? 200. What hindrance is overcome by Smee's battery ? How is it done ? 




Voltaic pile. 




VOLTAIC ELECTRICITY. 



89 




Smee's cell. 



Fig. 77. 



of gases to condense upon solid substances. In the battery a film 
of hydrogen forms in this way upon the smooth copper and pla- 
tinum, which is a serious hindrance to the action. If, however, 
the surface be roughened, it passes off with ease. Smee removed 
this difficulty by using a silver negative plate, and 
coating it with platinum black. To form the single 
cell, two plates of amalgamated zinc are clamped 
against a piece of wood with a silver plate between 
them, Fig. 76. They are then suspended in a glass 
vessel, the piece of wood resting upon the top. The 
liquid used is sulphuric acid diluted with ten or fifteen 
times its weight of water. A binding screw attached 
to the silver plate connects the positive wire, and an- 
other from the zinc plate the negative. A series of 
these cells properly joined, or a series of connected 
plates immersed in a suitable trough, constitutes Smee's lattery. 

201. Daniell's Battery.— Prof. Daniell 
made an important improvement in the bat- 
tery by using two different fluids separated by 
a porous partition. Fig. 77 exhibits a section 
of Darnell's cell ; a is an outer cylinder of 
copper filled with b, an acid solution of blue 
vitriol, which is kept saturated by crystals 
resting upon the perforated shelf/; c is a tube 
of porous ware, or unoiled leather, filled with 
d, 1 part of sulphuric acid to 7 water, and into 
this is plunged a rod of amalgamated zinc e. 
To the copper and zinc are attached binding 
screws for wire connections. 

202. The blue vitriol consists of sulphuric acid and oxide of 
copper. "When the action commences a double set of changes 
takes place in the liquid. Oxide of zinc is formed in the inner 
vessel, and the polarizing action taking place through the porous 
wetted body e, the sulphate of copper is decomposed in the outer 
vessel. The sulphuric acid set free is gradually transferred to the 
inner vessel, while the hydrogen, instead of being set free, com- 
bines with the oxy^n of the oxide of copper, precipitating metal- 
How is a single cell constructed? "What liquid is used? How are the wires at- 
tached ? 201. In what did Prof. Daniell's improvement consist ? Describe his 
cell. 202. Explain its mode of action. "Wliat is said of it? 203. How does 




Danieirs cell. 



90 



CHEMICAL PHYSICS. 



Fig. 78. 




Grove's cell. 



lie copper upon the surface of the outer cylinder. This was the first 
constant battery, and is capable of maintaining a uniform strength 
for many hours. 

203. Grove's Battery is also an arrangement for two fluids, 
like Daniell's, its metals being amalgamated zinc 
and platinum, and its liquids nitric and sulphuric 
acids. Fig. 78 is a vertical section ; a is a jar of 
earthenware, c the outer liquid of dilute sulphuric 
acid; l is a cylinder of amalgamated zinc con- 
nected with the negative electrode, and having a 
slit on one side to allow the free passage of the 
liquid. It is therefore exposed on both sides to 
the outer liquid c of dilute sulphuric acid ; d is a 
cup of unglazed earthenware filled with strong 
nitric acid e; f is a thin slip of platinum suspend- 
ed in the porous cup, and connected with the positive electrode. 

204. In Geove's lattery the oxygen combines with the zinc, 
as in the other cases, but the hydrogen decomposes the nitric 
acid, unites with a portion of its oxygen, forming water and 

producing deutoxide of ni- 
FlG - 79 - trogen, which rises into the 

air, and, reuniting with 
oxygen, forms nitrous acid 
fumes. The escape of 
these corrosive vapors is 
a disagreeable feature of 
this combination. Figure 
79 represents a series of 
cells in working connec- 
tion. Geove's battery pro- 
duces very powerful and 
brilliant effects, and is much used in telegraphy. It is less con- 
stant than Daniell's, but according to Prof. Jacobi, when the pla- 
tinum and copper surfaces are equal, that of Geove is 17 times 
more powerful. 

205. Bunsen's Carbon Battery is similar to Grove's, but re- 
places the expensive platinum by cheap carbon cylinders made by 




Grove's battery. 



Grove's battery differ from the preceding? 204. Explain its action. What is 
said of it ? 205. What is Bunsen's battery ? Of what does the Maynooth battery 



VOLTAIC ELECTRICITY. 



91 



pulverizing gas-carbon (526), mixing it with flour, and baking it 
into hard pieces. Dr. Callan's Maynooth lattery consists of a 
water-tight cast-iron cell, containing a porous cell, in which is a 
plate of amalgamated zinc. Mixtures of strong sulphuric and 
nitric acids are used, and the effects are claimed to be more in- 
tense even than those of Grove's battery. Schonbein's battery re- 
sembles the one just described, except that the outer cell is formed of 
passive iron, which makes an excellent combination with zinc (794). 

206. Resistance to the current. — As in machinery all the force 
applied is not available for work, some of it being absorbed by fric- 
tion, so all the electrical force generated in the battery cannot be 
made available for effect, a portion of it being destroyed by resist- 
ance of the materials of the circuit itself. The conductors are to a 
certain extent also obstructors. The resistance is, first, that of the 
liquid of the battery, which depends upon its conducting quality, 
and the distance between the plates. The larger the plates and 
the closer together, the less the resistance. Second, the wires 
offer a resistance dependent upon their length, narrowness, and 
material. 

207. Quantity and Intensity. — These terms describe two con- 
trasted states of electrical manifestation, the meaning of which 
may be illustrated by reference to heat. Thus the heat in the 
human body is considerable in quantity, but low in intensity, 
while that of an ignited match is very small in quantity, but high 
in intensity. Of course there can be no electricity that does not 
possess to a certain degree both qualities, but one or the other is 
always in great excess. 

208. In the battery the 
quantity of electricity depends 
upon the size of the plates ; 
the intensity upon the number 
of them. If we increase the 
size of a pair of zinc and cop- 
per plates, we increase the 
quantity of the electricity 
they produce, but not its in- 



Fig. 80. 




Accumulating intensity. 



consist? Schonbein's? 206. In what respect does the battery resemble ma- 
chinery ? Where is the resistance, and on what does it depend ? 207. What is 
meant by quantity and intensity in electricity ? Do they exist together ? 208. Upon 
what does the quantity of electricity in the battery depend? The intensity? 



92 CHEMICAL PHYSICS. 

tensity ; while, if we reduce the size, we reduce the quantity, the 
intensity remaining the same. On the contrary, if we multiply the 
number of pairs of equal size, the intensity is augmented at an 
equal rate while the quantity is unchanged. The electricity de- 
veloped by a single pair is exceedingly feeble; the second cell 
adds no more to it, but intensifies its power. In Fig. 80 the 
arrows illustrate the accumulating intensity. 

209. Frictional and current electricity. — It has been demon- 
strated that frictional and current electricity are one ; all the effects 
of the former being produced by the latter. But these modes of 
action are marvellously different. We may view a spark as a 
fraction of a current ; and a rapid succession of sparks as an imper- 
fect approach toward a current. But the duration of a spark is infin- 
itely small compared with the time necessary to accumulate the elec- 
tricity which produces it. A six-inch electric spark is estimated to 
pass in the three thousand millionth part of a second (Walker), 
but no frictional machine can supply a beginning to three thousand 
million such sparks in a second. The machine of the London 
Polytechnic Institute, with an 87-inch plate driven by steam at 80 
revolutions per minute, and a friction of 90 square feet of glass 
per second, gave the six-inch sparks no faster than they could be 
counted. The quantity is thus small, and the intensity high. But 
in the voltaic circuit, charge is as instantaneous as discharge ; the 
stream is unbroken ; the quantity is enormous, but the intensity 
low. 

210. A flash of lightning in a drop of water. — Dr. Faraday 
demonstrated that the electric current which is required to decom- 
pose a single grain of water is also sufficient to keep a platinum 
wire the f^th part of an inch in diameter red hot for 3| minutes. 
But to produce the same effect for the same time by frictional 
electricity would require 6,500,000 discharges from a Ley den jar 8 
inches high and 7^ inches in diameter. It would, therefore, require 
this amount of static electricity to decompose a single grain of 
water. Dr. Faraday further showed that this would suffice to 
charge an insulated conducting pane, such as a thunder-cloud, 

How may we vary either ? What does Fig. 80 represent ? 209. In what respects 
are current and frictional electricity alike ? How does the duration of a spark 
compare with the time required to accumulate it ? What instance is given ? How 
is it in the voltaic circuit? 210. How much voltaic electricity is required to 
decompose a drop of water? How much frictional electricity is this equal to? 



EFFECTS OF VOLTAIC ELECTRICITY. 



93 



Fig. SI. 



thirty-five acres in area, the instantaneous discharge of which 
would constitute a powerful flash of lightning. 

211. Voltaic electricity wiil travel through a conductor 
thousauds of miles rather than penetrate a harrier of air a small 
fraction of an inch in thickness, while static electricity will leap 
through miles. of intervening atmosphere. For sustained effects, 
as in chemical decompositions and telegraphy, where vast quantities 
of electricity are required, the battery is employed, its current 
being raised to the requisite tension by multiplying the cells. 

§ V. Effects of Voltaic Electricity. 

212. Decomposition of water. If the ends of the platinum 
wires connected with a battery are placed near each other in a 
vessel of water containing a little sulphuric acid to 
aid conduction, bubbles of gas will be seen to rise 
from the terminals and escape at the surface. A 
couple of glass tubes filled with water, and invert- 
ed in the vessel over the poles, serve to collect the 
rising gases, Fig. 81, which upon examination prove 
to be pure hydrogen and pure oxygen, the bulk of 
the former being twice that of the latter. The 
water becomes part of the circuit, and is decom- 
posed by a polarization of the line of compound 
particles between the electrodes in the same manner 
as occurs in the battery itself (195) ; only in this case, 
as the oxygen does not combine with the platinum, 
it is set free like the hydrogen. 

213. Electrolysis. — This operation is termed electrolysis (ana- 
lyzing by electricity), and any substance that is capable of this de- 
composition is called an electrolyte. Solids are not electrolytes. 
Liquids, and certain liquids only can be electrolyzed. A good 
electrolyte should be a good conductor, and yield upon separation 
a conductor and a non-conductor. The binary compounds are 
resolved into their elements by the current, and the salts into 
acids and bases. Sulphate of soda yields sulphuric acid at the -f- 
pole, where it may be made to redden vegetable blue, while soda 

211. How do they differ in power to penetrate the air? For what is the battery 
used ? 212. How is the decomposition of water effected by the current ? Explain 
Fig. 81. 213. What is electrolysis ? What bodies are good electrolytes ? Exam- 




Electrolysis of 
water. 



94 



CHEMICAL PHYSICS. 



appears at the — pole, and will there turn vegetable blues to red. 
By reversing the direction of the current, these beautiful effects 
are also reversed. • 

214. When compounds are electrolyzed their elements are 
found in opposite electrical states. Some, as oxygen, chlorine, sul- 
phur, appear at the positive electrode, and are called electro-nega- 
tive bodies ; while others, as hydrogen and the metals, appear at 
the negative electrode, and are called electro-positive. Of the 64 
elements, 24 are usually ranked as electro-negative, and 40 as 
electro-positive. Oxygen heads the first list, or is the most power- 
ful electro-negative body, while the newly discovered caesium 
heads the other, being the strongest electro-positive substance. 
The elements may be arranged in such an order that each will be 
electro-negative to all which follow it, and electro-positive to 'all 
which precede it. 

215. As the electric current thus originates in chemical changes 
and produces them, and as the atoms seem to be in opposite elec- 
trical states, it is obvious that electrical force is very closely allied 
to chemical power. The electro-chemical theory teaches that they 
are identical ; that electrical attraction causes chemical combina- 
tion, and that every chemical decomposition is due to the play of 
electrical forces. 

216. Electrotype is the name given to the pro- 
cess of depositing metals from their solutions by 
electricity. The deposited metal assumes with ex- 
actness the form of any body upon which it is made 
to settle, so that when removed it forms a perfect 
counterpart of the object, copying and reversing all 
its markings and irregularities. To copy a medal it 
is first made perfectly clean, and the back and edges 
protected by a coating of varnish or wax. The 
battery used may be of various forms ; Daniell's 
cell, Fig.. 82, answers the purpose. Into a glass 
tumbler, S, is introduced a lamp chimney, A P, with 
a piece of bladder tied oyer the lower end. This is 
filled with dilute acid, while the tumbler contains a strong solu- 



Fm. 82. 




Electro typing. 



pies. 214. How is the division of the elements into electro-negative and electro- 
positive effected? How are they proportioned to each other? How may the 
elements be arranged?. 215. What is the electro-chemical theory ? 216. What is 



EFFECTS OF VOLTAIC ELECTBICITT. 



95 



Fig. 83. 



tion of sulphate of copper. The medals m m are immersed in the 
sulphate of copper, and connected by wires to the zinc rod Z. 
Thus arranged, the sulphate of copper is gradually decomposed, 
and the metal evenly deposited. The copper coating is then de- 
tached, and forms a perfect reverse or mould of the object. The 
whole process is then repeated with the mould, producing an 
exact copy of the original medal. 

217. In electro-gilding and electro-plating the object is to 
impart a new and permanent metallic surface. In this way num- 
berless articles placed in solutions of silver and gold are coated 
with these metals, from the thinnest gilt to the thickest plating. 

218. Heating effects of the current. — A cur- 
rent passing through a conductor raises its tem- 
perature in proportion to the electricity arrest- 
ed. This depends first upon the quantity in 
motion, and second upon the resistance offered 
by the conductor. A wire which is but little 
heated by a current, if considerably reduced in 
diameter, becomes instantly white hot. The 
arrested electricity appears as heat. Two char- 
coal points brought into contact in the circuit, 
and then slightly separated, emit a light of daz- 
zling splendor, Fig. 83. 

219. The electric light.— -The brilliancy and 
purity of the electric light from charcoal points 
and the absence of contaminating products make it highly desira- 
ble as a source of illumination. But there is a mechanical difficulty 
in the way of its use. Particles of carbon are constantly transfer- 
red from the positive to the negative poles ; one is shortened and 
the other lengthened, and that unequally, so that it is trouble- 
some to maintain them at the precise distance. 

220. Blasting. — By passing a fine platinum wire through a 
charge of gunpowder, it is instantaneously exploded by the cur- 
rent. The same wire may pass through several charges and ignite 
them simultaneously. In excavating for an English railway, nine 
tons of gunpowder were buried in three masses in the Dover Cliffs, 




Electric light. 



the electrotype? Describe the process. 217. What is the object in electro- 
gilding and plating? 218. "When electricity is arrested by a conductor, what 
becomes of it? Upon what does the amount of heat depend? 219. What 
are the advantages and disadvantages of electric light ? 220. How is the electric 



96 CHEMICAL PHYSICS. 

from 50 to TO feet from the surface, and ignited by a distant bat- 
tery. The explosion detached 600,000 tons of the chalky cliffs. 
Powder is fired in the same way for blasting rocks under water. 

§ VI. Electro-Magnetism. 

221. In 1820, Prof. Oeested, of Copenhagen, discovered that 
if a magnetic needle be brought near a wire along which an elec- 
tric current is passing, the needle will be influenced and caused to 
move. The degree of the motion will depend upon the strength 
of the current, and its direction upon the relative position of the 
needle and wire. If the wire be above and parallel to the needle, 
the pole next the negative electrode will move westward ; if beneath 
the needle, it will move eastward. If the wire is on the east side, 

this pole will be elevated : if on the west, 
it will be depressed. In all cases it tends 
to place itself at right angles, or trans- 
verse, to the wire. If the wire be bent, 
so as to pass above and below the needle, 
Fig. 84, the effect is increased; and if it 
be coiled round many times in the same 
manner, it becomes still more powerful. The motion of a needle 
thus freely suspended becomes the visible test of an electric 
current. 

222. The Astatic Needle. — But a needle keeps its place in the 
magnetic meridian with considerable force, so that a very faint 
current will not move it. If two needles, however, are placed 
parallel, near each other, with reversed poles, their directive force 
is mutually neutralized. Two needles thus fixed upon an axis, 

Fig. 85, form the astatic (unstable) needle. If 
one is slightly stronger than the other, it still 
retains a feeble tendency to keep its north and 
south position. If now the wire of Fig. 85 
were folded round both these needles, the 
same current would urge them in opposite 
~J directions, and there would be no motion ; but 
Astatic needle. when the coil incloses only one of the needles, 
as the lower for example, the current impels 

current used in blasting? 221. What was Prof. Oersted's discovery? Upon what 
do the degree and direction of the motion depend? 222. What is the astatio 




JT 




ELECTRO-MAGNETISM. 



97 



Fig. ST. 



both needles in the same direction. If the needles be delicately- 
suspended, it affords the means of detecting the faintest electrical 
current and forms the galvanometer. 

223. Electro-Magnets.— If a bar of Fig. 86. 
steel be placed in a coil of wire, as in Fig. jh 
86, and a current be sent through the coil, 1 1 im^^iWM^M} 
the bar becomes at once permanently *\JUUUOOL/' r 
magnetic. If a bar of soft iron be intro- Magnetizing a Bar. 
duced, it becomes magnetic, but only continues so as long as the 
current is maintained. A horse-shoe bar of soft iron, with a wire 
twisted spirally round it, as in Fig. 87, becomes a 
powerful magnet, capable of supporting a heavy 
weight, while the current is passing. 

224. The Current a Magnet. — Electric currents 
attract and repel each other like magnets. "When 
two wires are freely suspended near each other, if 
currents pass through them in the same direction, 
they attract each other ; if in opposite directions, 
they repel each other. If a copper wire be coiled 
into a spiral, Fig. 88, and the extremity, a, hooks into 

a cup of mercury, while the other end dips into a second cup, the 
coil will be free to move in any horizontal direction. If now a 
current be transmitted through the 
coil, it arranges itself north and south, 
just like the needle, and it will be at- 
tracted and repelled by another simi- 
lar coil in the same manner as two 
magnets. Hence Ampere assumes that 
magnetic polarity is caused by electric 
influence,perpetually circulating round 
the particles of which the magnet is ^ ^ 

Composed. Polarity of the Current. 

225. Induced Currents. — If two conductors are placed near and 
parallel to each other, a current sent through one induces an op- 
posite current in the second. At the moment the circuit is form- 
ed and the primary current passes, a secondary current is produced 
in the opposite direction in the second wire. 




Fig. 88. 



fr 



needle ? What is the galvanometer ? 223. What do Figures 86 and 87 represent ? 
224. How do electric currents affect each other ? Explain Fig. 88, What does 
5 



98 



CHEMICAL PHYSICS. 



226. Electro-magnetic Telegraph. — This remarkable contri- 
vance consists of three parts : a battery for supplying the motive 
power, an insulated metallic line between the points to be con- 
nected, and an apparatus for signalling, or registering messages. 
Two wires were at first thought necessary to complete the circuit, 
but it was early found that the earth might be made to replace 
one wire if the other was connected with the ground at both 
ends. The electrical impulse which traverses the wire circulates 
round a bar of soft iron, magnetizing and demagnetizing it as often 
as the connection with the battery is made and broken, and thus 
motion is communicated to the recording machine. 

227. We must not forget that there is nothing like a current 
through the telegraph wires. We may be aided to understand 
what takes place by imagining a small tube, connecting two places, 
closely filled with a row of peas. As a pea is pushed in at one 
end, another falls out at the opposite end, although it is evident 
that nothing but motion has passed. But motion may pass 
although each pea keeps its position, if we suppose them all 
linked together by attractions upon their different sides. If the first 

pea were turned upon its centre, it would turn in 
like manner the whole series. The peas may 
represent the atoms of the telegraphic circuit, and 
their motions the polarization of particles by 
which the effect is communicated. The wire of 
the circuit communicates its polarity to the bar 
of soft iron around which it is wound ; this be- 
comes magnetically polarized, and attracts the 
marking lever of the recording machine. 

§ VII. Thermo-Electricity. 

228. The Thermo-electric Pile. — As electricity 
produces heat, so heat in turn produces electricity. 
A B, Fig. 89, is a bar of antimony, and B C a bar 
of bismuth soldered together at one extremity, 
and connected by the wire D at the other. When the place of 
junction is warmed an electric current is produced, which moves 



Fig. 89. 




Thermo-electric 
Pair. 



Ampere assume? 225. Explain what is meant by induced currents. 226. Of 
what parts does the electro-magnetic telegraph consist ? How is motion obtained ? 
227. Give the illustration of the peas. 228. Describe the thermo-electric pair, 



THERMO-ELECTEICITY. 



99 



Fig. 90. 



P 



Fig. 91. 



in the direction of the arrows. If the junction B is chilled, the 

current moves in the opposite direction. Such a combination 

forms a thermo-electric pair. The effect is increased if several of 

these are united, forming what is 

known as the thermo-electric pile. 

To secure a compact arrangement, 

they are soldered together as in Fig. 

90, and then combined as in Fig. 91, 

A representing one of the faces of 

the pile. When both faces are 

equally heated, there is no current. 

If the face, A, is warmed, there is a 

current in one direction due to the a (J 

difference of temperatures between 

the two faces. If the opposite face 

is warmed ; or, what is the same 

thing, if the face, A, is cooled, there 

is a reverse current. 

229. In Fig. 92, A B represents the thermo-electric pile as 

Fig. 92. 




Arrangement of the Bars. 




Thermo-electric Pile as mounted for use. 

mounted for lecture-room use. A shows one of the faces ; w w 
are wires connecting it with the galvanometer. The needle m n 

Fig. 89. Explain the construction and action of the thermo-electric pile. What 
docs Fig. 90 represent? 229. Describe the pile as mounted for lecture-room 



100 



CHEMICAIi PHYSICS. 



is suspended by a fibre S S of unspun silk, and protected from 
currents of air by the glass shade G. To one end of the 
needle is fixed a piece of red paper, and to the other a piece of 
blue. If the face of the pile is merely breathed upon, the warmth 
swings the needle round to 90°, or at right angles to the cur- 
rent, — the pieces of paper making the movement visible through- 
out the room. This important instrument was invented by Nobili, 
and applied with remarkable success to researches in heat by Mel- 
loni. It detects heat radiation from sources much lower than the 
human body, and announces the heat emitted from the bodies 
of insects. How wonderful, that the minutest quantity of heat 
we can detect, only appears after it has been first converted into 
electricity, then into magnetism, and then into mechanical motion ! 
230. As the earth constantly turns upon its axis, the sun heats 
its mineral constituents unequally, which must give rise to east and 
west electrical currents, and, as the magnet tends to place itself 
across them, we see the reason for the direction of the needle. The 
earth's magnetism appe irs thus caused by the action of the sun. 

231. Magneto-Electricity. — As electricity pro- 
duces magnetism, so magnetism may produce elec- 
tricity. If a bar of soft iron be introduced into a 
coil of wire, and a magnet be made to approach 
the bar, it is magnetized by induction, and at the 
same time a momentary current is produced in 
the surrounding wire. This is more simply shown 
by winding the armature of a horse-shoe magnet, 
Fig. 93, with a piece of copper wire, one end of 
which is flattened and the other sharpened. When- 
ever the armature is removed or replaced, a spark 
is produced at 0, indicating a current through 

Spark from Mag- the wire. 

232. Induction Coils. — If one or two hundred 
feet of stout copper wire are wound into a close coil, and then 
twenty or thirty thousand feet of much finer wire (both well cov- 
ered with silk) be wound into a secondary coil around the first, a 
current sent through the inner wire and rapidly interrupted, in- 
duces very powerful currents in the outer coil, which give rise to 



Fig. 93. 




use. What is said of it? 230. How is the direction of the needle explained? 
To what is the earth's magnetism due? 231. How may electricity be pro- 
duced by magnetism? 232. What is the principle of Ruhmkorff's coil? What 



ANIMAL ELECTRICITY. 



101 



Fig. 94. 



a stream of brilliant sparks. This is the principle of Ruhmkorff's 
coil, one of the most energetic electrical machines yet devised, pro- 
ducing electricity in large quantity and of extraordinary intensity. 
233. The Stratified Discharge. — If electricity be sent through 
an ordinary vacuum, the spark is changed to a diffused auroral 
glow. But when the vacuum becomes more perfect, the light 
appears stratified, or broken up into numerous rings or plates. 
Gassiot sealed platinum wire in glass tubes, and, by using an at- 
mosphere of carbonic acid which was first exhausted by the air 
pump, and the residue gradually absorbed by caustic potash, he 
produced a very perfect vacuum. "When the rarefaction is carried 
a step further than can be done 
with the air pump, on discharging 
a Huhmkorff coil through it, nar- 
row bands transverse to the line of 
discharge are seen, as in Fig. 94. 
Increasing rarefaction widens the 
bands, and gives them a conical 
shape, as in Fig. 95, and, as the 
vacuum becomes more perfect, a 
series of luminous cylinders of an 
inch or more in depth appear, di- 
vided by narrow dark lines, Fig. 
96, till at last, when the vacuum 
becomes perfect, discharge light 
and conduction cease. It seems thus proved that a vacuum, in- 
stead of being a good conductor, as was formerly supposed, is a 
perfect non-conductor, and that the presence of matter is indis- 
pensable to the manifestation of electrical force. 




Fig. 95. 






Fig. 96. 




Stratified Discharge. 



§ YIII. Animal Electricity. 

234. It was known to the ancients that certain fishes have a 
peculiar power of benumbing animals. It has been found that 
they possess electrical organs or batteries by which they can give 
powerful shocks, which produce all the effects of ordinary elec- 
tricity. Fig. 97 represents the torpedo with its electrical organs, 



is said of it ? 233. How does electricity appear in an ordinary vacuum ? When 
the vacuum is more perfect ? In the most perfect ? What does this prove ? 



102 



CHEMICAL PHYSICS. 



Fig, 97. 




Electrical Organs of the 
Torpedo. 



Fig* 98. 



a a, laid bare. They are^ situated on each side of the head, and are 
•composed of five or six sided prisms, ex- 
tending vertically from the lower to the 
upper side of the fish. They are divided 
in horizontal partitions, so that the whole 
resembles a mass of honeycomb, the cells 
being filled with a dense fluid consisting 
of water, albumen, and a small portion of 
common salt. These organs form a living 
lattery, and are the source of electrical 
force, just as the muscles are of mechan- 
ical force. A dense mass of nerves links 
them with the brain, which has control of 
the discharges the same as of muscular 
movement. The seat of control is the electrical lobe ; if this be 
uninjured the animal may be skinned, its heart cut out, and the 
other portions of the brain extirpated, without loss 
of the faculty. 

235. Galvani's well-known experiment with 
the frog was the starting-point of modern research 
in this branch of electricity. The legs of the frog 
are detached from the body, the skin removed, and 
the lumbar nerves exposed. They are then laid 
upon a glass plate with a small piece of zinc Z, Fig. 
99, placed under the nerve, while the feet rest on a 
thin slip of silver. They are dead and powerless, 
but if now a wire, W, be made to touch the pieces 
of metal, so as to form a connection between muscle 
and nerve, the legs instantly contract and kick away the silver. 
236. Human Electricity. — As it is now admitted that no 

chemical change can occur with- 
out electrical excitement, and as 
the human body is a mass of rap- 
idly changing chemical materials, 
it must be a theatre of extensive 
electrical movements, though to 




Brain of Torpedo. 

C, Cerebrum. 
O, Optic Lobe. 
E, Cerebellum. 
E, Elect. Lobe. 



Fig. 99. 




Experiment with Legs of Frog. 



234. Describe the electrical apparatus of the torpedo? What is its relation to the 
brain ? 235. What is said of Galvani's experiment ? How is it performed ? 236. 
What difficult problem is stated to be now demonstrated ? What has been proved by 
Matteucci ? By Dubois-Reymond ? What was his experiment with the frogs f 



THERMAL EXPANSION. 103 

demonstrate this has been one of the most delicate and difficult prob- 
lems of science. The blood is an alkaline liquid, while the juice 
of flesh is acid, and the two liquids are only separated by the thin 
walls of the vessels. By the action of these fluids there must be in 
every mass of muscle myriads of electric currents. Matteucci has 
proved that currents of electricity are always circulating in the 
frames of all animals, and that a positive current is continually 
passing from the interior to the exterior of a muscle. The smallest 
shreds of muscular tissue have been proved by Dfbois-Reymoxd 
to manifest currents, the longi- 
tudinal section being always 
positive to the transverse sec- 
tion. By arranging a series of 
half thighs of frogs, alternately 

connecting the exterior and in- Muscle Battery. 

terior surfaces, Fig. 100, he ob- 
tained a current that decomposed iodide of potassium, deflected a 
magnetic needle 90°, and caused the gold leaves of an electroscope 
to diverge. 




CHAPTEE IY. 

HEAT. 

§ I. TJiermal Expansion — Thermometers. 

237. This well-known force has an almost omnipotent con- 
trol over the states of matter ; it is an all-determining agency in 
nature, and is so essential to the numerous processes of the labor- 
atory that the chemist has been called the i Philosopher by Fire.' 
The general science of heat is termed Thermotics, from the Latin 
thermo, heat, which gives us also the words thermal, thermometer, &c. 

238. Expansion of Solids. — The general effect of heat upon 
matter is to expand it. The copper ball, Fig. 9, p. 36, when heated, 
enlarges and rests upon the ring ; when cooled, it shrinks and falls 

237. "What has the chemist been called, and why ? "What is thermotics, and whence 
is the name derived ? 238. What is the general effect of heat upon matter ? "What 




104 CHEMICAL PHYSICS. 

through it. The copper, and all bodies of uniform atomic condi- 
tion, expand equally in all directions, while other substances, as 
crystals and wood, in which the atoms are differently arranged in 
different directions, expand unequally (267). With a given amount 
of heat force, the same substance always 
expands to the same degree ; but the 
same quantity of heat causes different 
substances to expand unequally. This 
may be shown by riveting together thin 
slips of different metals, for instance 

Expansion of Compound Bars. , , . . . . , , . ^. 

brass and iron, into a straight bar, Fig. 
101. When dipped into hot water it is warmed, and the brass, 
expanding most, becomes longest ; the bar curves, the brass form- 
ing the convex side. If placed in ice water, the brass contracts 
most, and the bar curves in the opposite direction. Heat, which 
drives atoms asunder, is thus the antagonist force to cohesion : 
and a quantity of heat applied at a high temperature, produces 
more expansion than the same amount at a low one ; — the cohe- 
sion in the first case being partially overcome. 

239. The expansion of solids, though small, takes place with 
tremendous force. The Bunker Hill monument has a slight daily 
motion as the sun expands its sides. The ponderous iron tubes of 
the Britannia bridge lengthen and shorten, and writhe and twist 
like a huge serpent, under the varying influence of solar heat. 
One of the tubes, 400 feet long, is depressed in the centre but a 
quarter of an inch by the heaviest train of cars, while the sun, 
expanding its upper side from morning to noon, elevates it in the 
centre two inches and a half! Wheel tires and iron hoops are 

•made smaller than the frames they are to surround, and put on 
while red hot, their contraction on being suddenly cooled binding 
together the parts with great firmness. Iron, when joined with 
less expansible materials, as bars laid in masonry, often works 
serious injury by its expansions and contractions. 

240. Expansion of Liquids. — If the heat be sufficiently in- 
creased it overcomes cohesion, and the solid becomes a liquid. 
Liquids thus produced by heat, are also expanded by it, and to a 

bodies expand equally in all directions, and what unequally? What does Fig. 101 
represent ? What conclusions follow from this experiment ? 239. What illustrations 
are given of the expansive force of heat ? Why are wheel tires made smaller than the 
wheels they are to surround ? How do iron bars work injury in masonry ? 240. What 



THERMAL EXPANSION. 105 

much greater degree than solids. While iron increases from 
freezing to boiling but ¥ -L water expands ^ and alcohol J. 
Hence the seasons materially affect the bulk of spiritous liquors* 
.they measure five per cent, more in summer than in winter. By 
heating different liquids successively in a long-necked flask, Fig. 
8, p. 86, their relative expansibilities are shown. 

241. Expansion of Gases. — But liquids cannot be indefinitely 
expanded ; a sufficient repulsion of their atoms changes them into 
gases. As a general law gases expand much more than liquids, 
although certain liquids, as sulphurous and carbonic acids, are 
amongst the most expansible bodies known. As there are no 
varying cohesions to overcome, gases expand very nearly alike, 
increasing from the freezing to the boiling of water more than 
one third of their bulk. 

242. Measurement of Heat.— As the effect of heat is expan- 
sion, the measurement of expansion becomes the measurement of 
the force. The common instruments for measuring heat are called 
thermometers. They measure not quantity of heat, but temper a- 
ture. Heat is the force producing the effect ; and temperature 
the intensity with which it acts. The thermometer gives the 
same report of a gill of water as of a gallon ; their temperatures 
are the same, though one contains a far larger amount of heat 
than the other. Liquids are better adapted for thermometers 
than either solids or gases ; as in solids the expansion is too slight 
to be easily perceptible, and gases are too sensitive to changes of 
atmospheric pressure to fit them for this purpose. 

243. Mercurial Thermometer. — To make this instrument, a fine 
glass tube with a bulb upon the end is partly filled with mercury. 
The air is expelled from the rest of the tube by heating it till the 
mercury rises by expansion to the top, and at that moment the 
glass is hermetically sealed by melting the end of it with a blow- 
pipe. As it cools, the mercury falls in the tube, leaving a vacuum 
above. 

244. Mercury has several important advantages as a thermo- 
metric fluid. It is readily obtained pure, and does not adhere to 
the tube ; it is sensitive to heat, expands with greater regularity 

is said of the expansion of liquids? 241. How do liquids rank in expansibility ? 
Examples. Why do gases expand alike? 242. How is heat measured? "What 
are thermometers? "What do thermometers indicate? How are liquids best 
adapted for thermometers? 243. How is the mercurial thermometer made? 

5* 



106 



CHEMICAL PHYSICS. 



than most liquids, and has a range of 700 degrees between freez- 
ing and boiling. Temperatures below the freezing point of mer- 
cury are determined by thermometers filled with alcohol tinged 
with some coloring matter, to make it visible. 

245. The sealed tube is attached to a brass plate 
engraved with the thermometric scale, Fig. 102. It 
is then dipped into ice water, and a mark made op- 
posite the top of the column of mercury, called the 
freezing point. It is now introduced into boiling 
water, and the height to which the column rises 
is marked as the toiling point. These are natural 
standard points which serve as a basis for the 
division of the scale. In the Centigrade ther- 
mometer the freezing point is caDed zero, and the 
interval between that and the boiling point is 
marked off into 100 equal spaces called degrees. In 
Keatjmer's scale the same space is divided into 80 
degrees, and in both cases degrees below zero are 
distinguished from those above by prefixing the minus 
signs (-). 

246. The scale named after its inventor, Fahren- 
heit, and which has unfortunately come into general 
use in England and this country, is not so simple. 
He divided the space between freezing and boiling 
into 180 degrees; but, instead of starting at the 
freezing point, he thought he would find the lowest 
possible cold, and make that zero. So with snow 

and ice he got the mercury down 32° below the freezing point, 
and commenced counting there. On this scale, therefore, freez- 
ing occurs at 32°, and boiling at 212°. The several scales are 
distinguished by their initial letters F., C, and R. The Centi- 
grade, affording decimal subdivisions, is the most simple and 
rational, and is gradually coming into use for scientific purposes. 
But as Fahrenheit's thermometer is generally employed and 
most familiar, it will be the one referred to in this book when no 
other is mentioned. 

247. The Differential Thermometer consists of two thin glass 



Fig. 


102. 




\"**v 


' <3i 


W> ' 


aioC 


Eg 60 


— ft 


3— 


n?| 


E3 


=d 70 


c 


wr 


li 


53*60" 


4 


=j"40" 


9 


-S 


=d 30 


li 




32c 


i 


3 l0 
=3 ° 


1 


sp 


1 JO 

i 



Common Ther- 
mometer. 



244. What advantages has mercury as a thermometric fluid? 245. How are they 
marked ? What is the Centigrade scale ? Reaumer's ? 246. Describe Fahrenheit's 
scales. How did he get his zero ? What degrees are used in this work ? 247. Describe 



NATURE OF HEAT. 



107 




Differential Ther- 
mometer 



bulbs filled with air, and united by a bent tube containing a col- 
ored liquid, Fig. 103. If heat be applied to 
one bulb, the air within it expands and presses 
down the liquid, the degree of motion being 
shown by the scale. This thermometer, as 
its name signifies, merely denotes the dif- 
ference in temperatures between the two 
bulbs, and has only been useful in scientific 
researches. 

248. As mercury boils at 660°, temperatures above that degree 
are measured by the ex- 
pansion of solids. For Fig. 104. 
this purpose an instru- 
ment called the Pyrome- 
ter is employed. It con- 
sists of a bar of metal or 
clay, Fig. 104, one end 
of which is fixed, and the 
other joined to a lever 
which plays over a grad- 
uated scale, as the bar ex- 
pands or contracts. 




Pyrometer. 



§ II. Nature of Heat. 

249. Tne Caloric Hypothesis. — Having noticed the general ef- 
fects of heat, we may now inquire into its nature. The material 
hypothesis supposes it to be a kind of matter — a subtile fluid whose 
entrance into our bodies produces warmth, and its escape cold. 
This fluid — caloric, is supposed to be stored up in the interstices of 
bodies, some holding more than others, according to their capaci- 
ties. It is assumed to have an attraction for matter and to com- 
bine with it, whilst its own particles are self-repulsive, and thus 
cause the atoms with which they unite to repel each other. This 
hypothesis, from its simplicity, has done service in times past, but 
such has been the recent and rapid growth of knowledge, that, 
instead of any longer guiding to truth, it only eclipses it. 



the differential thermometer? 248. Describe the pyrometer. 249. What is the 



108 CHEMICAL PHYSICS. 

250. In judging of heat, we must not misinterpret its impres- 
sions upon ourselves. If we plunge one hand in ice water and the 
other in hot water, and then transfer both to water intermediately 
warm, it will seem hot to the one and cold to the other. Indeed, 
if we trusted our ordinary sensations, we should believe in two 
opposite principles of heat and cold, a doctrine which was long 
advocated until it was found that these are merely relative, and 
that cold is but the absence of heat. Intense heat and intense 
cold produce the same sensations ; frozen mercury blisters the 
flesh like hot iron. Putting aside then our sensations, what is it 
that we know concerning the nature of heat ? 

251. The Essence of Heat is Motion.— With a few exceptions, 
which are perhaps no real exceptions (485), the universal effect of 
heat upon all matter is to expand it. We say that bodies are heated 
and cooled, and that one warms another near it. But we strictly 
mean only that they expand and contract, and that a body in 
expanding contracts others, and in contracting expands them. 
Hence, divested of everything not belonging to it, we find the 
effect of heat to be simply a motion of expansion in matter com- 
municable from body to body. Thus the essence of heat is 
motion. The motion of a mass, implies the motion of its parts. 
If a body expands, it is because its atoms have receded farther 
from each other, that is, have moved. Heat is therefore such a 
motion among the atoms of a body as gives rise to expansion. 
This idea was clearly enunciated a hundred years ago by the 
philosopher Locke, who said, ' Heat is a very brisk agitation of 
the insensible parts of an object which produces in us that sensa- 
tion from which we denominate the object hot, so that what in 
our sensations is heat, in the object is nothing but motion.' 

252. Universality of Motion.— The later views of the forces 
compel the idea that the atoms of all matter are in a state of inces- 
sant movement. As nothing around us is at rest, the idea of the 
quiescence of atoms would seem to contradict the whole spirit 
and course of nature. The celestial bodies are in perpetual move- 
ment ; indeed each one has impressed upon it several motions. Our 



material hypothesis of heat ? How is it estimated ? 250. How may our sensations 
of heat mislead us? How are heat and cold related ? 251. What is the universal 
effect of heat ? When we say that bodies are heated and cooled, what do we strictly 
mean ? What is the essence of heat ? What kind of motion ? Give Locke's defi- 
nition of heat. 252. What idea results from the later view of forces ? What is 



NATURE OF HEAT. 109 

own globe has a motion of rotation upon its axis, lasting a day — a 
motion of translation round the sun, continuing for a year. It has 
also one motion upon its axis accomplished in 19 years, and an- 
other which is only completed in 25,868 years ; it has also a fifth 
motion with the solar system through space, which may require 
millions of years for its completion. Thus the character of the 
solar system depends upon the motions of the planets, which we 
may look upon as its atoms. 

253. It cannot be doubted that, at the other extreme of being 
among ultimate atoms, there is also an order of motions equally 
regular and systematic. Each atom, closely as it seems packed 
with its neighbors, is believed to be in a state of incessant vibra- 
tion, and all material bodies, however quiet and solid they appear, 
are supposed to be made up, nevertheless, of an infinity of these 
'whirling parts' which never touch each other and never rest. 
An atom may rotate upon its axis, oscillate, revolve through an 
orbit, or, like a planet, it may execute several of these motions at 
once. This idea has become the all-harmonizing principle of the 
forces. 

254. As heat is a motion of atoms, intensity of the motion de- 
termines temperature. When a body is heated, the vibration of 
its atoms is augmented ; the particles move through larger spaces ; 
are urged apart, and thus cause the body to expand in bulk. "When 
the vibrations of the atoms of solids become sufficiently violent, 
they are loosened from the rigid grasp of cohesion, and, continuing 
to oscillate as before, they are now at liberty to slip or flow around 
and among each other. This is the liquid state, in which rigidity 
has disappeared, although a certain amount of lateral cohesion still 
remains (64). A further augmentation of heat increases the swing 
of vibration until the atoms are thrown quite beyond the sphere 
of cohesion, and fly asunder into the vaporous or gaseous state. 
4 The ideas of the best-informed philosophers are as yet uncertain 
regarding the exact nature of the motion of heat ; but the great 
point at present is to regard it as a motion of some kind, leaving 
its more precise character to be dealt with in future investigations.' 

probable concerning atoms ? What is said of celestial motions ? 253. "What proba- 
bility does this create? "What view is held concerning the motion of atoms? 
254. What results from the intensity of atomic motion? When a body is heated, 
what occurs within? What results from the violent vibrations of the atoms of 
solids ? What causes the change from the liquid to the vaporous state ? What is 



110 CHEMICAL PHYSICS. 

255. The view just given is known as the dynamic hypothesis, 
or the mechanical theory of heat. That branch of the science of 
thermotics which treats of the laws of heat as a motive power, is 
known as thermodynamics, A difficulty in acquiring the new view 
is, that the current language concerning heat implies the material 
hypothesis. It is so natural to regard heat as a thing — to ascribe 
a substantive existence to that which is the subject of a name, that 
it will be necessary to guard against the misleading tendency of 
the ordinary terms. The pupil should strive to think of heat not 
as an abstract thing, but simply as a contagious or communicable 
motion of atoms. It may be further observed that this hypothesis 
is far from being new. It has been maintained by the acutest 
scientific intellects, as those of Bacon, Boyle, Newton, Mongol- 
fier, Seguin, Kumfokd, Davy, Leslie, and Young. But the late 
advances in the knowledge of force have brought it into a new 
prominence and caused its acceptance by the leading scientific 
minds of the age. {See note, page 173.) 

§ III. Sources of Heat 

256. The chief source of heat is the sun. As the stars are only 
remoter suns, we undoubtedly obtain from them a large amount of 
heat ; according to Pouillet, almost as much as from the sun itself. 
Combustion is a familiar source of heat which will be noticed here- 
after (579), and the vital heat of animals is due to the same cause 
(1257). Heat is also produced from the other forces — electricity, 
magnetism, and mechanical power. To consider the last-named 
source will aid us to clearer notions of the nature of heat and the 
true relations of the forces. 

257. The Heat of Friction. — Nothing is more familiar than the 
fact that friction produces heat. We warm our hands and ignite 
matches by rubbing them, whilst wood may be set on fire by the 
friction of one piece against another. The development of heat 
by friction may be strikingly shown by a simple mechanism. A 
hollow brass tube is mounted upright upon a table so as to revolve 
rapidly by turning a wheel. It is closed at the bottom, nearly 
filled with cold water, and tightly corked. The tube is then clasp- 

the important point in this connection ? 255. What is the view just given called ? 
"What is thermo-dynamics ? What difficulty is encountered here ? What should 
the student strive to do ? Is this hypothesis new ? Who have formerly maintained 
it ? How is it now regarded ? 256. What are the sources of heat ? 257. What 



SOURCES OP HEAT, 



111 



ed in a groove formed by two pieces of oak, T, Fig. 105, joined by 

Fig 105. 




Fig. 106. 



Machine for converting Mechanical Force into Heat. 

a hinge. Upon rapidly turning the wheel, the water is boiled, 
steam formed, and the cork exploded 20 feet into the air in two 
minutes and a half. Iron plates ground against each other by wa- 
ter have yielded a large and constant supply of heat for warming 
the air of a factory in winter. Heat is also produced by the fric- 
tion of fluids. Eennie inclosed 10 lbs. of water in a box, and, 
revolving it at the rate of 232 revolutions per minute, in a short 
time raised it to the boiling point. Hence water running in sluices 
and the sea after long storms are sensibly warmed. 

258. Compression al- 
so produces heat. A piece 
of cold wood or a cold 
leaden bullet squeezed 
forcibly in a hydraulic 
press are made warm. 
Percussion is another 
source of heat. A cold 
bullet struck upon an 
anvil by a sledge ham- 
mer is heated. A lead- 
en ball lifted several 
feet and dropped repeat- 
edly, is warmed ; and a 
cannon ball, when strik- 
ing an iron target or 
ship's side, is so intense- 




Mercury warmed by pouring it. 



examples are given of the heat of friction ? Describe the experiment. 258. Give 



112 CHEMICAL PHYSICS. 

ly heated as to produce a flash of light. The arrest of a liquid in 
motion is also a source of heat. If two glasses are swathed thickly 
round with listing, so that the warmth of the hand cannot affect 
them, and then cold mercury is poured from one to the other 
several times, Fig. 106, its temperature will be raised. 

259. What now is the source of heat in these cases? The ca- 
loric hypothesis utterly fails to explain it. That theory maintains 
that the heat of friction exists in a latent state in the bodies 
rubbed ; that different substances have different capacities for hid- 
ing and holding heat, and that friction diminishes this capacity, and 
thus brings it out, as squeezing brings the water out of a sponge. 
But this is grossly erroneous, as was proved by Davy. He rub- 
bed two pieces of ice together in a vacuum, and melted them by 
pure friction; but the water produced contained a far greater 
amount of heat than the ice, and the greater quantity could not by 
possibility be derived from the less. Besides, the amount of heat 
that various bodies naturally contain, as we shall soon see, is 
perfectly definite ; while, on the contrary, the heat produced by 
friction is inexhaustible, and is utterly independent of the nature 
of the substance used. This was demonstrated by Count Kum- 
foed more than sixty years ago. 

260. True Source of the Heat.-^The heat of friction depends 
not upon the properties of the bodies acting, but upon the force 
spent in producing it. The great principle has been established 
that force like matter is indestructible. It may be changed from 
form to form, but can neither be created nor annihilated — the 
total amount in the universe remains forever the same. Hence 
when a moving body is stopped, its force is not destroyed, but sim- 
ply takes another form. When the sledge hammer strikes the 
leaden bullet and comes to rest, the mechanical force is not anni- 
hilated, but is simply converted into heat, and if all the heat pro- 
duced could be collected, it would be exactly sufficient when re- 
converted into mechanical force to raise the hammer again to the 
height from which it fell. So when two bodies are rubbed to- 
gether, their surface particles are brought into collision, mecha- 
nical force is destroyed, and heat appears — the heat of friction. 

examples of compression and percussion. 259. How is this explained by the old 
hypothesis ? What is the bearing of Davy's experiment ? Why cannot the heat 
of friction proceed from the body itself? 260. Upon what does the heat of friction de- 
pend ? What great principle has been arrived at respecting forces ? When a moving 



SOURCES OF HEAT. 113 

261. We place a wheel upon a rough axle and set it to whirl- 
ing ; after a few turns it comes to rest, and the axle is found hot. 
The mechanical impulse has been converted by friction into heat. 
"We now lubricate the axle with some substance that reduces fric- 
tion, and set it to revolviug again with the same impulse. It now 
turns a much longer time, and the temperature of the axle is but 
slightly raised. Yet precisely the same amount of heat is gene- 
rated in this as in the other case, though the friction is now against 
the air and the heat escapes without detection. 

262. Take the familiar case of a railway train. Heat is gene- 
rated in the locomotive by combustion. A portion of it is wasted, 
and the remainder is spent in the expansion of water into steam, 
which through the machinery produces motion of the train. The 
object is to convert all the heat possible into mechanical motion, 
and so every rubbing surface is oiled, because each point of fric- 
tion is so much leakage and loss of motion by reconverting it into 
heat. But when the train approaches a station where it is desired 
to stop, what is to be done ? The moving force cannot be anni- 
hilated ; it must be transformed ; so the brakes are applied, the 
train slackens, smoke and sparks are produced, and the entire 
motion of the train is thus converted back again into heat. The 
rigorous relation of equivalency between heat and mechanical mo- 
tion will be considered hereafter (411). We only call attention 
here to the fact that the checking and arrest of mechanical 
motion, however slight it may be, whether of air, water, or solid 
bodies, is a definite and universal source of heat ; and again that 
heat, whenever it disappears, invariably produces some form of 
motion or work. 

263. Now as heat produces mechanical motion, and mechanical 
motion heat, they must clearly have some common quality. While 
heat was regarded as material, it was impossible to see anything 
in common between them, for how could the fall of a body, for 
instance, be converted into imponderable matter ? On the con- 
body is stopped, what becomes of its force ? How is the case of the sledge hammer 
explained ? When two bodies are rubbed together, what takes place ? 261. Explain 
the experiment with the wheel and axle. What becomes of the heat in the second 
case ? 262. What becomes of the heat in a moving locomotive ? What is the effect 
of the rubbing surfaces ? What occurs when the train is stopped? What is the 
universal relation of mechanical force to heat ? 263. How have they a common 
quality? What is the difficulty here in the material view? What does the me- 
chanical theory affirm ? When a moving mass is stopped by friction, what takes 



114 



CHEMICAL PHYSICS. 



trary, the dynamical theory affirms that as mechanical movement 
and heat are both modes of motion, they must be mutually and 
easily convertible. When a moving mass is checked or stopped, 
its force is not annihilated, but the gross palpable motion is in- 
finitely subdivided and communicated to the atoms of the body, 
producing increased vibrations which appear as heat. And so 
when heat produces work, as in the steam engine, a certain 
amount of it is destroyed, the motion of the atoms of steam being 
converted into mechanical motion of the piston and machinery. 

§ IV. Conduction and Convection of Heat. 

264. How it is Conveyed. — The closely packed particles of 
bodies cannot vibrate without communicating their motion from 
one to another. Each atom takes up the motion of its neighbors 
and imparts it to others, and thus the effect is gradually propa- 
gated through bodies ; this .is called conduction of heat. Bodies 
possess this power in very different degrees. If the particles vi- 
brate freely, they communicate their motion rapidly, and are said 
to be good conductors ; but if they are so trammelled that they 
cannot pass the motion freely, they are bad conductors. 

265. If several marbles 
are stuck by wax to a cop- 
per rod, Fig. 10*?, and heat 
be applied to one end, it 
gradually passes along the 
rod, the wax is melted, and 
the marbles drop off snc- 
sively. Generally the more 
dense a body is> the better it conducts ; 
therefore, solids are better conductors than 
liquids, and liquids than gases. As a 
class, metals are the best conductors, but 
they differ much among themselves in 
this respect. The imperfect conduction 
of liquids may be shown by filling a glass 
tube with water, inclining it over a lamp 
and applying the flame at the upper end, 
Non-conduction of Liquids. Fig. 108. The water will boil at the sur- 



Fig. 107. 




rr 



if 

Conduction of Heat. 



Fig. 108. 




place? 264. In what way does heat move through bodies? 265. Describe the 



CONDUCTION AND CONVECTION OF HEAT. 115 

face, while at the bottom there may still be ice for a considerable 
time. Dry air is one of the poorest conductors. Loose materials, 
as wool, cotton, sawdust, are bad conductors, chiefly owing to the 
air inclosed in their inner spaces. 

266. Connection of Heat and Electricity. — The following table 
shows the relative conducting properties of several metals, the 
power declining as the numbers decrease : 

Conductibility. 

Names or Substances. For Heat. For Electricity. 

Silver 100 100 

Copper 74 73 

Gold 53 59 

Iron 12 13 

Platinum 8 10 

German silver 6 6 

Bismuth 2 2 

The conducting power of the metals for electricity is also giYren, 
and a remarkable correspondence is seen in the numbers. Those 
properties which make a metal a good conductor of heat render it 
also a good conductor of electricity, and those which obstruct the 
one obstruct also the other. The forces must also be closely con- 
nected in their modes of action. 

267. Influence of Atomic Arrangement. — If the Fig.^09. 
atoms are disposed alike in all directions, conduc- ,A| 
tion is uniform, but, if there is a polar arrangement ^W^M„ 
of atoms, conduction "becomes unequal. This is " 
seen in crystals. A slice of quartz cut across its 
axis, Fig. 109,. was perforated with a small hole Equal Conduc- 
and covered with a layer of white wax. A wire 

was then inserted through the orifice and heated by an electric 
current. The wax melted in an exact circle, which showed equal 
conduction in all directions. A FlG 110 

slice cut parallel with the axis, 
as in Fig. 110, treated in the 
same way, gave an oblong out- 
line of the melted wax, showing 
that the heat travels with more 
facility along the crystalline axis 

,, m , . , , . Unequal Conduction. 

than across it. The metal bis- 





experiment with the marbles. How is the bad conduction of liquids shown ? 
266. How does silver differ from bismuth in conducting power? What relation 
between the conduction of heat and electricity ? 267. What condition of atoms 



116 



CHEMICAL PHYSICS. 



muth conducts both heat and electricity better along the planes of 
cleavage than across them. The same thing has been found in re- 
ference to wood ; it transmits heat better along the course of the 
fibres than across them. This principle economizes the warmth 
which the tree derives from the soil, by preventing its lateral es- 
cape, and at the same time protects the tree from the injurious ef- 
fects of sudden changes of external temperature. This effect is 
also heightened by the non-conducting bark. 

268. Conduction Influences Sensation. — The carpet feels warm- 
er to the naked feet than oil cloth, because the latter conducts 
away the heat faster from the skin, although both are at the same 
temperature. If the hand be placed upon silver at 120°, it will be 
burned, owing to the rapidity with which the motion of heat leaves 
the metal and enters the flesh. Water will not scald the hand if 
it be held quietly in it till it reaches 150°, while the contact of air 
at 250° or 300° may be endured. The principle of conduction is 
of great importance, not only in nature, but in its application to 
the arts and requirements of daily life. Nature protects the earth 
and crops from the excessive cold of winter by a layer of non- 
conducting snow; the birds she protects by feathery plumage, 
and quadrupeds by hair, wool, and fur. For winter clothing we 
select non-conducting textures ; but in summer, good conductors, 
as linen and cotton, to aid the escape of superfluous heat. 

269. Convection. — Although liquids and 
gases are poor conductors, yet from the mo- 
bility of their particles they may be rapidly 
heated by a process of circulation or con- 
nection. If heat be applied to the bottom 
of a vessel containing water, the lower por- 
tion of the liquid is warmed, expands, becomes 
lighter, and ascends, its place being taken by 
the colder liquid at the sides — thus forming' a 
set of currents which diffuse the heat through 
the whole mass. If a few particles of litmus 
be dropped into a flask of boiling water, the 
central current, made visible by the blue tint it has acquired, may 
be seen rising to the surface of the liquid, where it bends over in 



Fig. 111. 




Circulation of Heat. 



influences conduction? What is shown hy the experiments with quartz? What 
of wood ? How does this affect trees ? 268. How does conduction influence sensa- 
tion ? How is the principle employed in nature ? In art ? 269. How do liquids 



LATENT HEAT — INTERIOR WORK. 117 

every direction, Fig. Ill, and travels down the side of the vessel. 
In this way, water is circulated through systems of pipes to warm 
houses. 

270. Gases are heated in the same manner. The warm air in 
contact with a stove or other heated body becomes lighter, and 
ascends, while the colder and heavier air rushes in to supply its 
place. This, becomiug heated, also ascends, and thus a system of 
currents is established which diffuses warmth through the apart- 
ment. This principle is applied in warming houses with hot air, 
and also in arrangements for artificial ventilation. In the ocean 
and the atmosphere the same exchanges are incessantly going on, 
in the former giving rise to vast currents which equalize its tem- 
perature, and on land producing breezes, storms, trade winds, &c. 

§ Y. Latent Seat — Interior Work. 

271. Heat, by overcoming the cohesion of solids, detaches 
their atoms and changes them into liquids. That degree of heat 
which is required to liquefy a substance is called its melting point. 
From hundreds of degrees below zero up to thousands above, the 
various substances of nature melt at different temperatures, show- 
ing that each requires its particular amount of heat force to throw 
it into the liquid state. 

272. Latent Heat. — Whenever a solid is changed to a liquid, a 
certain amount of thermal force disappears in the process. If we 
apply heat to a lump of ice at 32°, it gradually melts, but the wa- 
ter produced is at the same temperature as the ice. What then 
has become of the heat ? In the language of the old hypothesis, 
the disappearing caloric is stored up in the water, where it still 
exists in a state of concealment as ' latent ' heat. But there is no 
evidence that it continues to exist as heat. According to the dyna- 
mic view, the heat does work by overcoming the cohesion of the 
particles, and is consumed in forcing them into new relations. 
This theory maintains that force cannot disappear without pro- 
ducing some effect ; it teaches that what is called ' latent ' heat 
is simply that amount of thermal force which is consumed in pro- 
convey heat? Describe the experiment. 270. How are gases heated? 271. Ex- 
plain melting points. 272. According to the old view, what becomes of the heat 
when ice is melted ? What evidence is there that it still exists as heat ? What is 



118 



CHEMICAL PHYSICS. 



Fig. 112. 



ducing effects different from heat, as fusion, evaporation, chemical 
changes, &c. 

273. If we expose equal weights of different substances to the 
same source of heat, they do not all receive it with equal readiness 

or in equal amounts in the same 
length of time ; some will become 
much warmer than others. If a 
cake of wax, D, Fig. 112, be 
placed upon the ring of a retort 
stand, and several metallic balls, 
having been immersed in a bath 
of hot oil, be placed upon it, they 
will sink through the wax at differ- 
ent rates'. The iron gets through, 
first, and the copper follows. The 
tin ball just peers through the 
lower surface, and is stopped, while 
the lead and bismuth scarcely 
sink to half the depth of the 
Hot Metallic Balls. c ^ e A i though t h e balls are all at 

the same temperature, yet they hold very unequal amounts of 
heat. Water requires 30 times as much heat as mercury to raise 
an equal weight of it through the same number of degrees. Hence 
bodies are said to have different capacities for heat, and, as each 
substance seems to require a particular quantity for itself, that 
quantity is called its specific heat. 

274. Calorimetry is the art of measuring the specific heat of 
bodies. This may be done in various ways : one is by observing 
the quantity of ice which equal weights of different substances 
melt in falling through equal degrees of temperature. The specific 
heat of water is found to be the highest of any known substance. 
Water being taken as 1, sulphur is 0.20, air 0.25, iron 0.11, copper 
0.09, and lead, mercury, and gold, 0.03. 

275. Twofold Action of Heat. — Thus when heat falls upon a 
body, a portion of it is manifested by the rising temperature, and is 
spent in producing increased vibrations of the atoms. But another 
portion is spent in forcing the particles of bodies into new posi- 




the dynamic view ? How does it regard latent heat ? 273. Describe the experiment 
of the cake of wax. What does this prove ? "What is capacity for heat ? Specific 
heat ? 274. What is calorimetry ? 275. When heat falls upon a body, what becomes 



LATENT HEAT — INTEKIOR WORK. 119 

tions, and as different substances have different atomic constitu- 
tions, different amounts of heat are consumed in acting upon them 
— these amounts are their specific heats. 

276. It has been well suggested that the atoms drawn together 
by cohesion resemble a weight pressed to the earth by gravity. 
With a cord and pulley we can overcome the gravity and raise 
the weight ; and we can also cause it to oscillate as it rises. One 
portion of the force is expended in raising it from the ground, and 
another in causing its vibrations. So with the atoms : at the same 
time that their vibrations are increased they are also forced into 
new arrangements. Heat consumed in this latter way is said to 
perform interior work. As the body cools, the constrained atoms 
gradually resume their former places, and the precise amount of 
heat is given out again. • 

277. Potential and Actual Energy. — When a weight is drawn 
up by a cord, it may be perfectly at rest, but the new position 
makes it a store of force, which in its fall becomes moving force. 
While suspended it was said to be in a state of possible or potential 
energy ; in falling, this is converted into actual energy. When 
it has fallen part of the distance, it is evident that a certain amount 
of potential energy is converted into actual energy; and, as it strikes 
the earth, all its potential energy is converted into actual energy. 
4 As potential energy disappears, actual energy comes into play ; 
throughout the universe, the sum of these two energies is constant? 

278. This principle applies equally to atoms ; the weight and the 
earth may represent two mutually attracted particles. The atoms 
of wood and coal are in the raised condition of potential energy ; 
oxygen may represent the earth ; they rush together in the fur- 
nace, and their potential energy is converted into the actual energy 
of heat. This again is spent in raising the atoms of water to the 
potential energy of steam. Again, the atoms of steam fall, and 
their potential energy is converted into the actual energy of the 
moving engine. 

279. Tremendous Energy of Atomic Movements. — As our or- 

: 1_ 

of it? 276. What do atoms attracted together resemble? How are the twofold 
motions illustrated? "What is interior work? 277. How does a weight suspended 
differ from one upon the ground? What is potential energy? Actual energy? 
Their relation ? 278. What is the condition of the atoms of wood and coal? How 
do they produce the actual energy of heat ? What becomes of the heat ? 279. How 
are we too apt to regard interior work ? What is the most impressive lesson of 



120 CHEMICAL PHYSICS. 

dinary conceptions of force result from the large effects that strike 
the senses, we very naturally conclude that the interior work per- 
formed by heat among insensible atoms is but a trifling affair ; but 
this is a grave mistake. The most impressive lesson of modern 
science is, that the material objects around us which appear so pas- 
sive are, nevertheless, filled with the most tremendous activities. 
A pound of iron upon being heated from freezing to boiling expands 
■$ls of its length. The atoms are but slightly shifted, yet the heat 
necessary to move them would raise 8 tons one foot high ; or, in 
other words, the heat exerts a force upon the iron 16,000 times 
greater than that of gravity. 

280. In melting 9 lbs. of ice, heat changes the position of the 
atoms, and confers upon them the potential energy of water. Ad- 
ditional heat drives the atoms further asunder, and confers upon 
them the higher potential energy of steam. Still further heat (or an 
equivalent force) decomposes the steam, forming 1 lb. of hydrogen 
gas and 8 lbs. of oxygen gas, with a still higher state of potential 
energy. Now, in returning to their former conditions, they give 
out an actual energy exactly equal to their potential energy. The 
clashing force of the atoms, as they revert to the successive states, 
has been represented by the fall of a weight down three great pre- 
cipices. The first fall — the collision of the two gases — is equal to 
the plunge of a ton weight down a precipice 22,320 feet high ; 
the second fall — the condensation of the steam — is equal to the 
descent of a ton down a precipice 2,900 feet high ; and the third, 
the freezing of the water, is equal to the fall of a ton weight down 
a precipice 433 feet high. 

281. Prof. Tyndall remarks, 'I have seen the wild stone ava- 
lanches of the Alps, which smoke and thunder down the declivities 
with a vehemence almost sufficient to stun the observer. I have 
also seen snowflakes descending so softly as not to hurt the fra- 
gile spangles of which they were composed ; yet to produce from 
aqueous vapor a quantity of that tender material which a child 
could carry, demands an exertion of energy competent to gather 
up|the shattered blocks of the largest stone avalanche I have ever 
seen, and pitch them to twice the height from which they fell.' 

modern science? What are the comparative effects of heat and gravit}' upon a 
pound of iron? 280. What changes does heat work in nine pounds of water? 
What are the steps of potential energy which the atoms ascend ? To what is their 
actual energy equal ? 281. What striking illustration does Prof. Tyndall give of the 



LIQUEFACTION — FREEZING EBULLITION. 121 



§ VI. Liquefaction — Freezing — Ebullition. 

282. The amount of force consumed in producing liquefaction 
is readily ascertained. If we take an ounce of ice at 32°, and one 
of water at 174°, and put them together, when the ice is melted, 
we shall have two ounces of water at 32°. The ounce of hot 
water has therefore parted with 142° of its heat in melting the 
ice, which amount is the ' latent heat ' of the resulting water. 
Those who have attempted to melt snow for domestic purposes 
know by the delay in the result the great loss of heat involved. 

283. We here note the beneficial influence of thermal laws 
in the world's economy. If when ice is at 32°, the addition 
of one degree of heat would raise it to 33°, and thus throw it 
into the liquid form/ all the accumulated snows of winter might 
be turned almost in an hour into floods of water, by which whole 
countries would be inundated. But so large an amount of heat is 
required to produce this change, that time must become an element 
of the process ; the snows are melted gradually in spring, and all 
evil consequences are prevented. 

284. Freezing Mixtures. — Advantage is taken of the absorp- 
tion of heat in liquefaction to produce freezing mixtures, the most 
common example of which is snow and ice. In this case the salt 
melts the ice to unite with its water, which in turn dissolves the 
salt, so that both solids are changed to liquids. These changes 
require great heat, which is absorbed from surrounding bodies; 
the cold produced sinking the thermometer 40° below zero. 
Four ounces each of sal ammoniac and nitre finely powdered, and 
mixed with eight ounces of water, will reduce the temperature 
from 50° to 10°. A convenient method of freezing a little water 
is to drench powdered sulphate of soda (Glauber's salt) with 
muriatic acid ; it may sink the thermometer from 50° to zero. 

285. Heat Liberated by Freezing — If the change of a solid to 
a liquid consumes force, the reverse change must produce it ; the 
force therefore reappears as heat upon freezing. As the thawing 
of snow and ice in spring is delayed by the large amount of heat 
that is expended in the forming of water, so the freezing processes 

power of molecular forces ? 282. How is the heat of liquefaction found ? 283. What 
are the effects of this principle ? 284. How do snow and ice produce cold ? Men- 
tion another freezing mixture. 285. How is freezing a warming proeess? Its 
6 



122 CHEMICAL PHYSICS. 

of autumn are delayed, and the warm season prolonged, by the 
large quantities of heat that escape into the air, from the changing 
of water into ice. The same principle is made available to pre- 
vent the freezing of vegetables, fruits, &c, in cellars, during in- 
tensely cold weather. Vessels of water are introduced, which, in 
freezing, give out sufficient heat to raise the temperature of the 
room several degrees : freezing is thus made a means of warming. 

286. Regelation. — Attention has lately been called to the fact 
that if pieces of moistened ice are brought into contact, they 
freeze together; lumps swimming in water — even warm water — 
may be made to cohere. This phenomenon is called regelation. 
The surface particles of the ice gain their liquid freedom, because 
they are confined only on one side, but when the surfaces are 
brought together, this liberty is instantly checked ; what was the 
surface becomes the centre, and cohesion takes place. Ice crushed 
to fragments can be refrozen in a few seconds under hydraulic 
pressure into a solid transparent mass, taking the shape of the 
mould in which it is pressed. It has long been a^natter of inquiry 
by what property of ice those frozen rivers, the glaciers, slowly 
move along their tortuous beds, down the sides of mountains. It 
has been attributed to a viscous property by which the ice flows 
like thick tar; but regelation — the property of crushing and 
freezing under pressure — seems better adequate to explain the 
facts. 

287. Ebullition. — When water is gradually heated, minute 
bubbles are found at the bottom of the vessel, which rise a little 
way, are crushed in, and disappear. These consist of vapor or 
steam, which is formed in the hottest part of the vessel, but as 
they rise through the colder water above, are cooled and con- 
densed. The singing sound of vessels upon the fire just before 
boiling is supposed to be caused by vibratory movements pro- 
duced in the liquid by the formation and collapse of these vapor 
bubbles. As the heating continues, these rise higher and higher 
until they reach the surface and escape into the air, producing 
that agitation of the liquid which is called boiling or ebullition. 

288. The temperature at which this takes place is called the 
boiling point. Different liquids boil at different temperatures, but 



effect in nature? 286. What is regelation? How are glacial motions explained? 
287. What ii tbo cause of boiling ? 288. What is the boiling point ? What causes its 



LIQUEFACTION — FREEZING EBULLITION. 123 

each liquid has a boiling point peculiar to itself. This varies with 
circumstances ; it is slightly influenced by the nature of the con- 
taining vessel. To glass and polished metallic surfaces liquids 
adhere with greater force than to rough surfaces ; and before 
vapo4zation can occur, this adhesion must be overcome. Sub- 
stances dissolved in a liquid also raise its boiling point on account 
of their adhesion. Under ordinary circumstances, water boils at 
212°, but saturated with common salt its boiling point is 224°. 
It has lately been shown that the amount of air dissolved in the 
water affects its boiling point, as it presses the watery particles 
asunder, and thus aids them to take on the gaseous state. Water 
purged of its air by long ebullition has been heated to 275° 
without boiling. "When it did boil the water was instantly 
changed into vapor with a loud explosion, the cohesion of its 
particles being suddenly overcome, like the snapping of a spring, 
by the repulsive power of the accumulated heat. The explosion 
of steamboat boilers, it is thought, may sometimes be owing to 
this cause. 

289. But the" most important circumstance that influences the 
boiling point is the pressure of the atmosphere. This resists the 
rising vapor, and as it fluctuates, the boiling point varies. At the 
level of the sea, atmospheric pressure is about 15 pounds upon 
every square inch of surface, and its variations make a difference 
of 4J degrees in the boiling point. This pressure 
becomes lighter as we ascend into the atmosphere, 
and the temperature of the boiling point is corre- 
spondingly diminished, so that boiling water is less 
hot in high altitudes than in low ones. At the 
hospital of San Bernard on the Swiss Alps, which 
is 8,400 feet above the sea, water boils at 184°. 

290. The Culinary Paradox affords as triking 
illustration of the boiling of water at a low tem- 
perature under diminished pressure. A flask half 
filled with boiling w^ater is tightly corked and in- 
verted upon the ring of a filter stand, Fig. 113. 

The pressure of the confined steam will cause the boiling instantly 
to cease. If cold water be now poured upon the flask, the steam 



variation ? What is the effect of removing air from -water ? 289. How does pres- 
sure affect the boiling point ? How ascending a mountain? 290. What is the 




124 



CHEMICAL PHYSICS. 



Fig. 114. 




Pulse Glass. 



Fig. 115. 




within will be condensed, the pressure relieved, and boiling will 
commence energetically. If again hot water be poured upon it, 
by renewing the steam and the pressure, the boiling ceases. The 
pulse glass is a tube connecting two bulbs, and half filled with 
ether, air being excluded. On grasping one of the bu&s, the 

heat of the hand so expands the 
ether, that its vapor forces the 
liquid into the other bulb with 
violent ebullition, Fig. 114. 

291. The Spheroidal State.— 
Water adheres to most surfaces, 
but heat destroys this attraction, and, if drops of it fall upon a red- 
hot plate of metal, they gather into spheroids, roll about, and 
evaporate very slowly. Fig. 115 represents a 
mass of water in the spheroidal state. In this 
case the heat of the metal produces a layer of 
vapor which supports the drop, so that it does, 
not touch the surface, but is driven about by 
a current of heated air. The temperature of 
the spheroid never reaches the boiling point 
of the liquid, as the vapor, being a non-con- 
ductor, does not transmit the heat from the 
metal, and besides, it is kept cool by evapora- 
tion from its surface. If the temperature of 
the plate be allowed to fall to a point at which 
the water wets its surface, it will be suddenly 
scattered in a kind of explosive ebullition, Fig. 
116. 

292, All volatile liquids act in this respect 
like water. Liquid sulphurous acid, when 
poured into a red-hot crucible, takes the sphe- 
roidal state, and, as its boiling point is 18° below the freezing point 
of water, we can actually freeze water by pouring it into sulphurous 
acid in a red-hot crucible. We can thus explain another remark- 
able fact. If damp with perspiration, or slightly moistened, the 
hand may for an instant be dipped in melted lead, or white-hot 
melted iron, without burning or discomfort. The thin film of 

culinary paradox ? The pulse glass ? 291. What is the spheroidal state ? How is 
the spheroid supported ? Why does it not boil ? Why does it explode ? 292. How- 
may water be frozen in a red-hot crucible? What facts does this explain? 



Spheroid of Water. 



Fig. 116. 




Its Explosion. 



VAPORIZATION. 125 

moisture is thrown into the spheroidal condition, and presents an 
effectual barrier against the intense heat. 



§ TIL Vaporization. 

293. The change of solids or liquids by the force of heat to va- 
por is called vaporization. Substances which are readily converted 
into vapor are said to be volatile, while those which are vaporized 
with difficulty are termed fixed or non-volatile. The slow forma- 
tion of vapor from the surfaces of bodies is called evaporation. It 
goes on at all temperatures, even from the surface of ice and snow, 
but is rapidly increased as the temperature rises. 

294. Heat of Vaporization.— A much larger amount of heat is 
spent in converting liquids into vapors than in changing solids to 
liquids, while the vapors are no hotter than the liquids from which 
they are formed. The heat has been consumed in producing the 
repulsive motion and the consequent enormous expansion of the 
gaseous body. If the liquid is exposed to the air, it is impossible 
to raise its temperature above its natural boiling point. All the 
heat added after boiling commences is carried away by the vapor. 
Water boiling violently is not a particle hotter than that which 
boils moderately. 

295. The quantity of heat which disappears during evapora- 
tion is very large. With the same intensity it takes 5 J times 
as long to evaporate a pound of water as it does to raise it from 
freezing to boiling ; it hence receives 5£ times as much heat. If 
therefore 180° were required to boil the pound of water, nearly 
1,000° are necessary to change it to vapor, and being spent in 
producing the change of state, it of course disappears. This quan- 
tity is, therefore, the c latent ' heat of steam. If the process be re- 
versed and the vapor be made to reassume the liquid form, the 
heat reappears. The condensation of a pound of steam will raise 
5 1, pounds of water from the freezing to the boiling point. Steam 
is hence a valuable agent for transporting heat, as is done by steam 
pipes for warming buildings. 

296. Its Cooling Effects. — As evaporation consumes heat, it is 

293. What is vaporization ? Evaporation ? 294. What is said of the heat required f 
How is it consumed ? Why does not boiling water grow hotter ? 295. How much 
heat is required to vaporize a pound of water ? What is the latent heat of steam ? 
If the steam is condensed, what follows ? 296. Mention some of the cooling effects 



126 



CHEMICAL PHYSICS. 



Fig. 117. 



a cooling process. We experience this in the cold sensation of 
evaporating a few drops of ether from the hand. As the per- 
spiration evaporates from the skin, it becomes a powerful cool- 
ing agency and regulator of bodily temperature, while the vapor 
which escapes from the breath, by its absorption of heat, exerts a 
cooling effect within the body. It is interesting to observe how 
the great capacity of water for heat makes it so gratefully cooling 
as it enters the body, and how its still greater capacity for heat 
when passing into vapor enables it so constantly to bear away 
from us the germs of fever as it escapes from the system in the 
form of insensible or manifest perspiration. The pernicious effect 
of wearing wet clothing arises from the rapid evaporation of its 
moisture, which robs the body of large quantities of heat. Damp 
soils are cooler than dry ones, because evaporation dissipates the 
heat which falls upon them. The heat of torrid regions would 
be insufferable, were it not for the cooling 
effects of rapid evaporation. Wind hastens 
evaporation, as it carries away the air as soon 
as it is laden with moisture, replacing it with 
drier air. 

297. Freezing by Evaporation. — Water 
may be frozen by its own evaporation, as may 
be seen in the experiment, Fig. 117. A vessel 
of water and another of sulphuric acid are 
placed under a bell jar from which the air is 
exhausted. The sulphuric acid absorbs the 
moisture of the water so rapidly that the lat- 
ter is soon frozen. 

293. The Cryophorus or Frost Bearer is 
an instrument which strikingly illustrates this 
principle. It consists of a tube with a glass 
bulb at each extremity, one of which con- 
tains a little water. Air is expelled from the 
instrument by boiling the water, the aperture 
through which the steam escapes being seal- 
TheCryophorol ed, while the remaining space is filled with 
vapor. The empty bulb is then placed in a 
freezing mixture, Fig. 118, and the vapor condenses, its place being 

of evaporation. Why is wet clothing injurious? 297. How may water be frozen 
by evaporation ? 298. Explain the principle of the cryophorus. 299. How and by 




Freezing Water. 



Fig. 118. 




VAPORIZATION 



127 



Fig. 119. 



supplied by vapor from the water bulb. Condensation and evapo- 
ration go on so rapidly that the water is soon frozen. 

299. The greatest artificial cold has been produced by the rapid 
evaporation of highly volatile liquids. By the vaporization of car- 
bonic acid and ether in the vacuum of an air pump, Faraday reach- 
ed 166° below zero, while, by mixing liquid protoxide of nitrogen 
with bisulphide of carbon in a vacuum, M. Natterer produced 
the lowest recorded temperature, 220° below zero. 

300. Moisture in the Air.— The air always contains moisture, 
tne amount of which varies with the temperature. The power 
of the air to absorb moisture is called its capacity for absorption. 
When it contains as much as it is capable of holding at a given 
temperature, it is said to be saturated, and any lowering of the 
temperature condenses it in the form of clouds, mist, fogs, dew, &c. 
The degree of temperature at which the mois- 
ture is condensed is called the dew point. 
If the temperature of the air has to fall but 
a few degrees before moisture is deposited, 
the dew point is said to be high, and there 
is much moisture in the air ; while, if the 
temperature must fall far, the dew point is 
low, and the air contains less moisture. It 
is obvious, therefore, that, by finding these 
two points of temperature, one can easily 
obtain the amount of atmospheric humidity. 

301. Hygrometers are instruments for 
measuring atmospheric moisture. The one 
most generally used is the wet bulb hygrom- 
eter, Fig. 119, and consists of two thermom- 
eters, one of which shows the tempera- 
ture of the air. The bulb of the other is 
covered with muslin, which is kept con- 
stantly moist by a string leading from it to 
a reservoir of water below. Evaporation 
takes place from the moistened bulb at a 
rate which depends upon the dryness of the Wet Bulb Hygrometer. 



whom have the lowest degrees of cold been found ? 300. Upon what does the 
amount of moisture in the air depend ? What is the effect of lowering its tempera- 
ture ? What is the dew point ? Meaning of high and low dew points ? SOI. What 
are hygrometers? Explain the principle of the wet bulb hygrometer. 302. Of 



128 



CHEMICAL PHYSICS. 



Fig. 120. 




air ; and by the coldness thus produced the mercury in the ther- 
mometer is correspondingly depressed. By comparing the differ- 
ence between the two thermometers at any time, and referring to a 
table, the quantity of moisture in the atmosphere is ascertained. 

302. Daniell's Hygrometer, Fig. 120, is 
a beautiful instrument for determining the 
dew point, constructed on the principle of 
the cryophorus. The long limb ends in a 
glass bulb Z> half filled with ether, into 
which dips a small thermometer. The butt) 
a on the short limb is empty and covered 
with muslin. The temperature of the air 
is shown by another thermometer, c, affixed 
to the stand of the instrument. When an 
observation is to be made, a little ether is 
poured upon the muslin, and, as it evapo- 
rates, the temperature of the other bulb be- 
comes reduced. "When it is sufficiently cold 
Danicirs Hygrometer. , ,, . , « , , ... .-n 

to condense the moisture of the air, it will 

be covered with dew. The thermometer in the tube & shows at 
what temperature this deposition takes place, and of course gives 
the dew point. This instrument is more accurate than the former. 
The amount of moisture in the air of our artificially heated rooms 
is a matter of great importance to health, and the hygrometer is 
very valuable in enabling us to determine it. 

303. Volume and Density of Vapor. — Equal bulks of different 
liquids generate unequal volumes of vapor. Water yields a larger 
amount than any other liquid. .^ While a cubic inch of water gives 
1,694 inches of vapor, a cubic inch of alcohol yields 528, one of 
ether 298, and of oil of turpentine 193. But the less the volume 
of vapor, of course the greater its density. While 46.6 cubic 
inches of turpentine vapor weigh 68 grains, the same bulk of ether 
weighs 37, of alcohol 23, and of watery vapor but 9 grains. The 
density of vapor is increased, %fther by cold or pressure. The point 
at whicn its temperature cannot be further lowered without re- 
turning to the liquid state, is called its maximum density. 

304. Its Elastic Force. — All vapors are elastic, and have a 



Daniell's hygrometer? 303. How much vapor is produced "by a cubic inch of 
water? Of alcohol? Ether? Oil of turpentine? How do their densities com- 
pare ? What is the maximum density of vapor ? 304. What is the elastic force of 



VAPOEIZATION. 



129 



Fig. 121. 



tendency to diffuse themselves through space, exerting more or 
less force against any obstacle that resists their expansion. This 
expansive force of vapors is called their elastic force or tension. 
In the barometer, a column of mercury 30 inches high is driven 
into the tube by the pressure of the air (563). It, therefore, re- 
quires a force of 15 lbs. per square inch to press the mercury all 
out of the tube. If a little water be introduced under the bottom 
of such a tube, it rises to the surface of the mercury, and in the 
vacuum above exhales into vapor with a sufficient force to press 
the mercury down below its former level. But the amount of this 
elastic force depends upon the temperature. At 36° below freezing, 
although the water is changed to ice, it still gives off a vapor of 
force sufficient to depress the mercury ^ of an inch ; at 36° it 
sinks it | of an inch ; at 80°, 1 inch ; at 179°, 15 inches ; and at 
212° the mercury is pressed entirely out of the tube, proving that 
the elastic force of the vapor at 212° or boiling point equals the 
atmospheric pressure. Different vapors have 
different degrees of elastic force. At 80° the 
vapor of alcohol depresses the column 2 inches, 
and that of ether 20 inches. 

305. As the temperature rises above 212°, 
the elastic force increases, and the boiling point 
becomes higher and higher, as is proved by 
an apparatus called ' Marcet's Digester,' Fig. ^ 
121. This consists of a small globe of iron or 
brass, with three apertures, through one of 
which a thermometer is passed, air tight ; 
through the second, a long glass tube, open at 
both ends, and reaching nearly to the bottom 
of the vessel ; while the third is furnished with 
a stopcock. To the tube is attached a scale 
divided into inches. Mercury is now poured 
in, sufficient to cover the end of the tube, and the globe is half 
filled with water, in which the thermometer bulb is immersed. 
Upon applying heat with the stopcock open, the water boils at 
212°, and the steam is driven out against the pressure of the at- 
mosphere. But if the stopcock be closed, the temperature begins 
to rise ; the steam being confined, its tension increases, and the 

vapor ? How may it be ascertained ? 305. What are the parts of Marcet's appa- 
ratus ? What takes place when heat is applied with the stopcock open ? With it 
6* 




Marcet's Digester. 



130 



CHEMICAL PHYSICS. 



mercury begins to be pressed up the tube. At 249.5° the mer- 
cury will have been driven up 30 inches, and the pressure is equal 
to an additional atmosphere ; at 356.6° it is equal to 10 atmospheres, 
and at 415.4° it is equal to 20. 

306. Steam. — It is well known that the expansive force of heat, 
acting through the vapor of water, is the impelling power of the 
steam engine. In low-pressure engines, steam is used from below 
the pressure of the atmosphere up to 20 or 30 lbs. per square inch 
above it, while high-pressure engines employ steam of 70 or 80 
lbs. pressure to the inch. It has been noticed that gases expand 
equally by equal additions of heat, the proportion being about $%■$ 
part of their volume with each degree of temperature. But with 
steam in contact with water and constantly generated, it is not the 
case. With equal additions of heat, the expansion is more rapid 
at high temperatures than at low ones ; hence there is an econ- 
omy of force in using high-pressure steam. With low pressure 
there is an economy of heat and fuel, but, as the steam, instead of 
being driven out, is condensed into water, the necessary apparatus 
renders the engine complicated and cumbrous. Steam separated 
from water expands uniformly like gases, and may part with its 
additional heat without being condensed. When it is thus sepa- 
rated, and receives an extra charge of heat, it is said to be super- 
heated. At high temperatures, it is used to carbonize wood and 

disorganize animal matter, which it 
does, by reducing the flesh to a fluid 
mass, the bones being separated in a 
state of powder. It may be heated 
sufficiently hot to melt lead. 

307. Distillation consists in vapor- 
izing a liquid by heat in one vessel, 
and condensing it by cold in another, 
Fig. 122. The object may be either 
to separate a liquid from non-volatile 
substances dissolved in it, as in distil- 
ling water, to purify it from foreign 
ingredients, or to separate two liquids which evaporate at differ- 
ent temperatures, as alcohol and water. In the latter case, the 

closed ? 306 What steam pressures do different engines employ ? How is high- 
pressure steam economical ? What are the advantages and disadvantages of low- 
pressure engines ? What is superheated steam ? What is it used for ? 307. What 



Fig. 122. 




Distillation. 




VAPORIZATION. 131 

heat is carried just high enough to vaporize the least volatile 
liquid. The product of the process is called the distillate. When 
solids are vaporized, the process is termed sublimation, and the 
condensed vapor a sublimate. 

308. Condensation of Gases. — When a gas loses heat enough to 
•change it to a liquid or solid state, it is said to be condensed. The 
distinction between gases and vapors was formerly supposed to be 
that the latter are condensible into liquids, while the former are not. 
But under the joint influence of pressure and extreme cold, many 
gases once considered permanent have been reduced to liquids, and 
some even to the solid state. Dr. Faraday effected this by a very 
simple method. He placed the materials from 

which the gas was to be generated in one end 
of a glass tube bent in the middle, which was 
then hermetically sealed, Fig. 123. The ex- 
panding gas confined in so small a space ex- 
erted a tremendous pressure, the force of which 

..... _. . _ . _ Condensation Tube, 

condensed a portion of it into a liquid m the 

other end of the tube, which was immersed in a freezing mixture 
to facilitate the process. By this method, and at a temperature of 
- 166°, he succeeded in liquefying carbonic acid, chlorine, ammonia, 
and several other gases. More recently M. Batterer, of Vienna, 
applied a cold of - 220° and a pressure of 3,000 atmospheres; but 
some of the gases, as oxygen, hydrogen, nitrogen, carbonic oxide, 
refused to liquefy, even under this tremendous force. It is sup- 
posed, however, that, under the proper conditions of cold and 
pressure, all gases could be made to assume the liquid or the solid 
state. 

309. Radiant Heat is a branch of thermotics usually treated in 
this connection ; but it is a mode of action so closely linked with 
light, that we shall obtain a clearer view of its nature by con- 
sidering them together. This will be especially proper, as a chief 
purpose in treating of the forces is to bring out the idea of their 
intimate connections and correlations. 

is distillation? Its object? What is sublimation? 308. What was the former 
distinction between vapors and gases ? Does it still hold ? How did Dr. Faraday 
effect the condensation of gases? How fnr has M. Natterer gone with these 
experiments. 309. Why is radiant heat deferred? 310. What is the common 



132 CHEMICAL PHYSICS. 

CHAPTEE V. 

LIGHT — THE RADIANT FORCES. 

§ I. Movements of Light. 

310. In its common, restricted meaning, light is that agent 
which, acting on the eye, produces vision, and the general laws 
of its movement belong to optics. But science has shown that 
the solar ray, instead of being simple, is a sheaf of diverse forces 
which produce the most extensive and varied changes, physical 
and chemical, upon the surface of the earth. These effects, though 
of different kinds and differently named, are all due to one mode 
of action ; they have a common explanation, and hence require to 
be considered together. Light is called a radiant force, because 
it moves in rays ; other forces, moving in the same manner, are 
also called radiants or radiations. 

311. Decrease of Intensity.— Light moves in straight lines, and 
in all directions from the point of emission. As it radiates away, 

it diminishes in intensity as the square of the dis- 
tance from the point of emission ; that is, at a 
distance of two feet the light will be four times 
less intense than at one foot ; at three feet it has 
but one ninth the intensity, as shown in Fig. 124, 
^1 ^"+"^9 where the upper figures represent the distances, 

Decreasing intensity, and the lower ones the corresponding intensities. 
It has been proved in various ways that this force 

moves through space with the velocity of 192,000 miles per second 

312. How Light is Received.— When it falls upon bodies, it is 
either thrown back from them (reflected), extinguished by them 
(absorbed), or passed through them (transmitted). Those which 
transmit it, as air and water, are termed transparent ; those which 
admit it only partially, as rough glass, or oiled paper, are called 
translucent, while those which refuse to transmit it are said to be 
opaque. We can see objects through a transparent substance,* but 

notion of light? How is it regarded by Science? To what are the effects due ? 
What are radiant forces? 311. At what rate does light diminish in intensity? 
What is its velocity ? 312. How do bodies receive light ? What is transparency ? 




MOVEMENTS OF LIGHT. 



133 





Reflection of Light. 



only light through a translucent one. The body traversed by light 
is called a medium. ~No medium is perfectly transparent ; even 
the purest air absorbs a portion of the light in its passage through 
it. Nor are any substances absolutely opaque ; even gold in thin 
films transmits a greenish light. 

313. Reflection. — When a ray of light strikes perpendicularly, 
or at right angles upon a polished surface, FiG 125 

as at a &, Fig. 125, it is thrown back in ex- 
actly the same line; but if it fall ob- 
liquely, it is reflected obliquely, as is shown 
by the arrows. The angle of rebound is 
equal to the angle of striking, or, as it is j 
commonly expressed, the angle of reflec- 
tion is equal to the angle of incidence. 

314. Refraction.— When light passes from one medium to an- 
other of a different density, as from air to water, it is liable to be 
turned out of its straight direction. If its course be 
perpendicular, as a 5, Fig. 126, it will not be divert- 
ed ; but if it fall obliquely, as at c d, it will be re- 
fr acted, and proceed to e. If the refracting me- 
dium have parallel surfaces, the ray on leaving it is 
again bent back to its original course, as is seen in 
the figure. For this reason, common window panes, 
which consist of plates of glass with parallel sur- 
faces, produce no distortion in the appearance of 
objects seen through them. If we partly immerse a stick in water, 
it will seem bent or broken at the point of entrance, owing to the 
rays from the immersed portion being refracted as they pass from 
the water to the air. The refracting power varies in different 
substances, generally increasing with their density. It, therefore, 
forms one of the distinguishing properties of bodies, and is fre- 
quently used as a test of chemical purity, as in detecting the adul- 
teration of essential oils, when other modes would prove insuffi- 
cient. 

315. The Analysis of Light.— By the prism — a triangular piece 
of glass, or other transparent substance — the sheaf of rays is un- 




Refraction. 



Translucency ? Opacity? A medium? 313. By what law is light reflected? 

314. What is refraction ? What causes the broken appearance of an oar in water ? 

315. How is light affected by the prism ? What is the spectrum ? What is the 



134 



CHEMICAL PHYSICS. 







bound, and spread out before us. A beam of solar light pass- 
ing through such a prism, Fig. 127, is refracted by it, and pro- 
duces an oblong colored image 
FlG * 127 * called the solar spectrum. It is 

usually considered to comprise 
the seven colors enumerated 
in the accompanying diagram. 
White light is, therefore, held 
to be a compound consisting of 
these colored lights, which are 
only separated by the prism. 
Each color has its own peculiar refrangibility, or degree of di- 
vergence from the original source, the red being least refracted, 
and the violet most. The separation of the colors in the spectrum 
is called dispersion, and transparent substances differ much in this 
power. A hollow glass prism filled with oil of cassia gives a spec- 
trum (1), Fig. 128, more than twice the length of that produced by 
flint glass (2). 

Fig. 12S. 



Decomposition of Light. 



1 


L B 


C D 


E r G TT 


1 


m 


i _jm 


2 




I i 




i mm wmmm 



ABCDEF G II 

1. Spectrum from prism of oil of cassia. 2. From flint glass. 

The letters correspond to certain fine dark lines which cross the spec- 
trum and serve as its permanent landmarks. These lines are hence 
more separated in the highly dispersed spectrum (1) than in (2.) 

316. The separate colors cannot be again decomposed; hence 
they are called primary. Newton, who first decomposed the ray, 
assumed that there are seven ; Brewster holds to three primaries — 
red, yellow, and blue, the remaining colors being compounded of 
these. Herschel says any three colors of the spectrum may be 
taken as primary, and all the others compounded from them by 
the addition of white ; while Prof. Baden Powell remarks, ' The 
fact is, the number of primary rays is not really seven, but infinite.' 



separation of colors in the spectrum called ? What is the effect of the oM-of-cassia 
prism? 316. Why are the colors called primary? What was Newton's view of 
the constitution of the spectrum ? Brewster's? Herschel's? Baden .Powell's? 



THE WAVE THEOEY. 135 



§ II. The Wave Theory. 

317. The old hypothesis of light assumed it to consist of moving 
particles, or corpuscles, shot from the luminous source, which pass 
through transparent bodies, rebound from reflecting surfaces, and 
entering the eye, produce vision by striking against the optic nerve. 
But the luminous ray produces a variety of effects — heat and chem- 
ical force as well as light, with various kinds and gradations of 
each, and the foregoing explanation is profoundly insufficient to ac- 
count for all these complex and wonderful phenomena. Evidently 
there is but one principle of action among all the forces of the 
ray : the key to light and color must also unlock the mystery of the 
thermal and chemical radiations. We have this explanation in the 
wave theory of light. 

318. Motion of Sound. — Sound is a radiation ; it proceeds rap- 
idly in straight lines in all directions from the point of emission ; 
is reflected and refracted according to the same laws which govern 
the other radiant forces, and may be passed through lenses and 
conveyed to focal points like light. But sound is proved to be a 
motion of waves or undulations transmitted through the air. Here 
then is a principle of nature employed to produce the kinds of ef- 
fect with which we are dealing. 

319. Wave Motions.— TV ith these we are all familiar. If 
one extremity of a long 

cord, Fig. 129, be briskly FlG - m 

moved up and down, | g 
wave-like motions pass 
rapidly from one end to 

_ 1 \ _. . Undulation of a Cord. 

the other. The parti- 
cles which compose the cord do not advance; they only move 
from side to side ; the undulatory motion alone flows on. If we 
toss a stone into still water, waves arise at the point of disturbance, 
and pursue each other in rapidly extending circles ; there is no 
current ; light objects are not drifted forward ; the water particles 
only rise and fall while the wave progresses. By wave length is 

317. What is the old hypothesis of light? "What must a true theory of light 
explain ? 318. How does sound move ? In what way is it propagated ? 319. What 
does the cord illustrate ? What is it that goes forward ? Describe the motion of 
water waves. How do the water atoms move ! What is a wave length ? 320. How 




136 CHEMICAL PHYSICS. 

here meant the distance from the crest of one wave to that of the 

next, or from depression to depression, as from a 
Fig. 130. , , ' 10 _ \ , , ^ 

y to 6, Fig. 130, or from c to a. 

p^ ,^A ? ^20. Sound Waves.— So also a vibrating so- 
lj|lifa||iiiM norons body, as a bell, throws the aerial particles 
W^ve^n*th * nto a gi ta ^ on ? an ^ tne nndulations sent through 
the air breaking upon the nerves of hearing, the 
effect is transmitted to the brain as sound. A harp' string, for ex- 
ample, is vibrated, and as it advances, it crowds together or con- 
denses the air particles before it ; as it retreats, the air particles 
behind it separate more widely, and a rarefaction occurs. Ad- 
vancing again, another condensation is produced ; and again re- 
treating, there is another rarefaction. A condensation and a rare- 
faction constitute a sound icave — its length being the distance from 
the centre of one condensation to the centre of the next, or from 
the centre of one rarefaction to that of the next. These pulses are 
propagated through the air at the rate of 1,100 feet per second. 

321. It is marvellous how slight an impulse throws a vast 
amount of matter into tremulous motion. We may easily hear 
the song of a little bird 500 feet above us ; but before that note 
could have travelled to our ears, it must have filled with wave 
pulsations a sphere of air 1,000 feet in diameter, or have thrown 
into agitation nearly 18 tons of atmospheric gases.* 

322. The pitch of sound depends upon frequency of vibrations. 
The quicker a string vibrates, the more rapidly will the pulses fol- 
low each other ; the shorter will be the wave, and the higher the 
sound. Hence, the violinist, to produce a higher note, shortens 
the string by pressing his finger upon it. Shrill notes are caused 
by rapid vibrations, while the low notes result from those which 
are slower. The lowest note of a 7-octave piano is made by 32 
vibrations per second; the highest by 7,680, while each interme- 

* Guns are fired in the Alps to start avalanches by the concussion of the air, 
and it is said that great masses of snow are often poised with such perfect equi- 
librium that the sound of the voice alone is sufficient to dislodge them. Speaking 
of the chamois hunters, Rogers says ; 

1 From rock to rock, with giant bound, 
High on their iron poles they pass ; 
Mute, lest the air, convulsed with sound, 
Rend from above a frozen mass.' 

is sound produced ? How does a harp string affect the air ? What is a sound 
wave ? Its length ? Velocity ? 321. What is said of the power of a little bird to 
agitate the air ? 322. Upon what does pitch depend ? How are sharp notes caused ? 



THE WAVE THEORY. 137 

diate note has its fixed number. Intensity or loudness of tone de- 
pends upon the intensity with which the air is struck by the vi- 
brating body, or the amplitude of the excur- 
sions of the vibrating particles. A string ' 
that swings from a to b, Fig. 131, will pro- ^-- Jf"*«n. 

duce a louder sound than if vibrating no ^> : - ~^-X 

farther than c, though the pitch will be in gweep of y ibratl0IL 
both cases the same. 

323. Ether. — Now the radiant forces are believed to be all 
propagated by undulatory motions ; but motions in what ? Sound 
has its medium — the air ; and the sound rays cannot cross a vac- 
uum, as there is nothing to convey them. But heat, light, and the 
chemical force dart through the most perfect vacuum we can pro- 
duce, and traverse in all directions the interstellar spaces. There 
must be something throughout these spaces to transmit the mo- 
tion. The wave theory of light assumes the existence of a univer- 
sal ether — an infinitely rare and elastic medium which is diffused 
through nature, pervading even the most solid bodies. It con- 
nects atom with atom and star with star. Through this universal 
medium — the dynamic bond of nature — waves are sent with a velo- 
city far exceeding those of sound. 

324. It is objected to this idea of ether that it is a pure crea- 
tion of fancy, like caloric and phlogiston (579). It is urged that 
as we know the forces only as manifested in matter, and as a 
perfect vacuum has never been produced, it is better to assume 
that some form of actual matter is universal, and that the wave 
motions take place in that. But it is after all very much a ques- 
tion of terms. Both views assume a universal medium capable of 
transmitting undulatory motions ; one calls it material, an^d the 
other ethereal. Ether is not held to Ins force, but only the medium 
for representing those motions by which force is transmitted. 
One ether suffices for all the forces, and thus by introducing the 
idea of unity in their modes of action, we are prepared to com- 
prehend their mutual relations. While the theory of ether may 
be objected to on some grounds, yet it is a vast advance on former 

"What is said of the piano? What is intensity ? How illustrated ? 323. What is 
believed of all the radiant forces? Why is there probably a universal medium? 
Describe the ether. Its uses. 324. What objection is made to ether? What has 
to be assumed at any rate? What is ether held to be? Whal is gained by the 
conception ? What has an eminent authority remarked, and why ? 325. How is 



138 CHEMICAL PHYSICS. 

ideas, and so combines and explains a multitude of facts which 
cannot be otherwise accounted for, that an eminent authority has 
remarked, ; If it is not true, it deserves to be ! ' 

325. Cause of Colors. — According to this view, light is trans- 
mitted by ethereal undulations just as sound is by those of the 
atmosphere ; with only this difference, that while the air particles 
move backward and forward in the same direction as the advan- 
cing wave (normal vibrations), the ethereal particles move across 
the course of the wave (transverse vibrations). Thus the spec- 
trum is to the eye what the gamut is to the ear. As the pitch of 
sound depends upon the length of the air wave, so the color of 
light depends upon the length of the ethereal wave ; and as loud- 
ness of sound depends upon the extent of the swing of air parti- 
cles, so the brightness or intensity of color results from the extent 
of the excursions of the ethereal particles. 

326. By several refined methods which cannot be detailed 
here, the lengths of the ethereal waves upon which colors 
depend have been rigorously established. The motions which 
produce red are slower, and the undulations longer than those 
which produce violet. It is found that 39,000 waves of red light 
would measure an inch, while 57,500 waves of violet light would 
fill the same space. The other colors are intermediate, their num- 
ber of waves increasing gradually from red to violet. As light 
moves 192,000 miles per second, that length of ray streams into 
the eye each second. If this distance be reduced to inches, and 
the product be multiplied by 39,000, we shall have the number of 
waves which beat against the retina each second, when we look 
upon a red color. If the same product is multipled by 57,500, we 
get th^e number of pulses per second which strike the retina when 
looking upon a violet color. If a single second of time be divided 
into a million of equal parts, a wave of violet light trembles or 
pulsates in that incredibly short interval, 727,000,000 times ! If 
these results seem incredible, we should remember that we are 
dealing with the resources of the Infinite. In treating of atoms 
we saw the minuteness of the scale upon which nature divides her 
spaces, and here we have her corresponding infinitesimal scale of 
time and force. 

the motion of light explained? Difference between light and sound motions? To 
"what is the spectrum compared ? Upon what do color and brightness depend f 
326. What are the lengths of the red and violet waves ? What is the velocity of 



THERMAL RADIATIONS. 139 

327. It is necessary to distinguish between vibrations and 
undulations ; the former take place among the atoms in all kinds 
of matter, the latter only in the transmitting medium. In the 
case of sound, the vibrations of a sonorous body produce undula- 
tions in the air, which, when falling upon other bodies, may set 
them also to vibrating. So the vibration of atoms in a flame, 
produces undulations in the ether ; these are transmitted to the 
nerve of vision, and, breaking against it, throw its atoms into the 
vibrations which produce sight. 

323. The nerves of hearing can be acted upon only by a cer- 
tain range of air pulsations. There are air waves which fall upon 
the ear in regular recurrence, but exert no sensation ; they are 
either too slow or too fast. It is probable that the hearing organs 
of different animals have still different ranges of sensibility, per- 
ceiving sounds which are too high or too low for the human ear. 
Just so with the ethereal undulations ; the nerve of the eye is 
adapted to a certain range of pulsations, and waves too slow or 
too rapid do not awaken the sensation of light. 

329. The colored spectrum, Fig. 127, embraces the range of 
ethereal undulations which produce luminous effects : below it 
are waves too slow to act upon the eye, while above it they are 
pitched too high. We shall soon refer to still niore remarkable 
analogies between sound and light. But it is really no more ex- 
traordinary that myriads of ethereal waves beating incessantly 
upon the retina, should awaken the sensation of vision, than that a 
storm of air waves pouring upon the ear, perhaps from a hundred 
instruments at once, should give us the experience of music. 
Nature produces the most varied results by the simplest means ; 
conveying to us harmony and beauty— the anthem and the land- 
scape by the same method. 

§ III. Thermal Radiations. 

330. Heat is associated with light ; it moves with the same 
remarkable velocity ; is weakened by diffusion at the same rate, 
and is reflected, absorbed, transmitted, and refracted by various 

light? How many inches per second? How many red waves enter the eye 
each second? Of violet? 327. What is the distinction between vibrations and 
undulations? 328. What is said of the range of audible sensation ? 329. Is the 
eye sensitive to all ethereal waves ? What is said of the unity of nature's methods ? 



140 



CHEMICAL PHYSICS. 




Reflection of Dark Heat. 



Fig. 133. 



bodies in accordance with the same laws as light. When thus 
moving, it is called radiant heat. 

331. Luminous and Obscure Heat. — Radiant heat is of two 

kinds : that which accompanies light is called luminous heat ; that 

which is emitted from dark bodies, as a stove below redness, is 

• termed obscure heat. That dark 

radiations of heat obey the 
same laws of motion as light, 
may be proved by placing a 
warm iron ball, c, Fig. 132, 
opposite the thermo-electric 
pile p, the conical reflector be- 
ing turned away, so that no di- 
rect heat can reach it from the 
ball. A bright tin screen, m n, 
is then so placed that the angle made by the incident heat from 
the ball shall be the same as that reflected from the tin surface 
which strikes the pile. The moment the screen 
is placed in position, the needle of the galva- 
nometer starts, showing that reflection has taken 
place. 

332. Thermal Spectrum.— "When a ray of light 
is decomposed by the prism, it is found that the 
heat is refracted like light, and is distributed 
through the colors, but the refrangibility is lower, 
and dark heat is therefore found below the red 
ray. The thermal spectrum was first traced by 
Sir John HePwSchel, and found to have the out- 
line represented in Fig. 133, its lower part being 
curiously discontinuous. 

333. How Radiation takes place. — We can 
now explain thermal radiation in harmony with 
the later views of the nature of this force. As 

heat consists in the vibration of the particles of common matter, 
this motion is communicated to the ether in which they are im- 
mersed, and propagated through it exactly in the manner of light. 
The ethereal pulsations, striking against other substances, increase 

330. What are the analogies of the motion of heat and light ? What is radiant 
heat ? 331. What is luminous heat ? Obscure heat ? What does Fig. 132 illus- 
trate? 332. What is the thermal spectrum? 333. How is the radiation of heat 



Thermal Spectrum. 



THERMAL RADIATIONS. 



141 



the vibration of their particles, and thus heat them. As a body- 
cools, it loses atomic motion — the ether transmits this motion, and 
other bodies acquiring it are thereby warmed. 

334. Exchanges of Heat. — All bodies, though at a hundred de- 
grees below zero, contain some heat ; that is, their atoms are all 
in vibration, though at varying rates. This motion must be com- 
municated to the ether, so that all bodies radiate heat at all times, 
and are hence constantly exchanging it with each other. If a can- 
non ball at 1000° be placed beside another at 100°, it parts with 
its own motion rapidly to the other, as illustrated by the radiant 

Fig. 134. 




Fig. 135. 



Exchanges of Heat. 

lines, Fig. 134. But the ball at 100° also radiates its motion, 
though more slowly, thus returning a portion to the hotter ball ; and 
if a ball of ice were added, 
the same thing would take 
place, only in a feebler de- 
gree. If a body receives 
motion faster than it com- 
municates it, its tempera- 
ture rises ; if the reverse, 
it cools, and if the ex- 
changes are equal, there is 
equilibrium, or a uniform 
temperature. Hence, other 
things being equal, the rate 
of radiation depends upon 
temperature. 

335. Influence of the 
Surface. — But thermal ra- 
diation is also influenced by surface. 




Radiation from Leslie's Cube. 



In Fig. 135, o represents a 



explained? What is the part played by the ether? 334. Why must bodies con- 
stantly exchange heat ? What does Fig. 134 illustrate ? What is the cause of 
equilibrium ? 335. How do surfaces influence radiation ? What are the best 



142 CHEMICAL PHYSICS. 

cubical vessel of pewter with one of its sides coated with a layer of 
gold, a second with silver, a third with copper, and a fourth with 
varnish. The vessel is then filled with hot water, and placed at a 
little distance from the thermometric pile p. When the hot gold 
surface is turned to the pile, scarcely a trace of effect is observed, 
and so with the copper and silver ; but when the varnished sur- 
face is brought round, a stream of heat strikes the pile, and the 
needle is driven round against its stops. The condition of the sur- 
face also influences radiation — rough, uneven surfaces being more 
active than bright polished ones ; hence, if the metal is covered 
with woollen or velvet, its radiant power is increased. Bright 
metallic vessels, therefore, retain the heat much longer than those 
which are tarnished. 

336. Absorption. — Good radiators are good absorbers of heat; 
that is, the surfaces which can easily communicate motion to the 
ether are equally capable of accepting it from the ether. On the 
contrary, a bad radiator, as a bright metallic surface, is a bad 
absorber, and therefore a good reflector. Hence, the thinnest 
metallic film upon a surface powerfully protects it from the action 
of radiant heat. 

337. As bodies differ widely in their atomic condition, it is not 
to be expected that they will all act alike upon the ether ; some 
will communicate more motion than others. This explains the dif- 
ferent radiating and absorbing action of bodies. Atoms vibrating 
singly cannot impress as much motion upon the ether as vibrating 
groups, or systems of atoms. The atoms of the elements — gold, 
silver, copper — vibrate singly, and disturb the ether but slightly ; 
while those of varnish, flannel, or velvet oscillate in masses, and 
transmit an increased amount of motion. 

338. Influence of Color.— According to Melloni, color exerts 
no influence upon the radiant power of surfaces ; white, black, 
and red radiating alike, so that as regards the loss of heat from this 
source, the color of our clothes is of no importance. On the con- 
trary, color powerfully influences the absorption of luminous heat. 
Dr. Fkankxin spread differently colored pieces of cloth upon the 
snow in the sunshine. The black sunk farthest, that is, melted 
most snow, and, of course, received most heat. The blue piece 

radiators ? The purest ? 336. How are radiation and absorption related ? 
337. What are we to expect from the atomic peculiarities of bodies ? What kinds 
of atoms affect the ether least ? What most ? 338. How does color affeet radia- 



THERMAL RADIATIONS. 143 

sunk to a less depth, the brown still less, and the white hardly at 
all. Hence by scattering soot over snow its melting may be 
hastened. Darkening a soil in color, is, therefore, equivalent to 
moving it farther south, and, for the same reason, black clothes 
absorb most solar heat. 

339. Dew. — When the radiation of bodies is not compensated, 
their motion is gradually spent upon the ether, and their temper- 
ature sinks. Such is the case with objects exposed to the sky on 
clear nights. If good radiators, they rapidly lose heat, and, cool- 
ing below the temperature of the air, at length begin to condense 
its moisture upon their surfaces : this is dew. The best radiators, 
as grass, leaves of trees, and porous soils, receive the most dew, 
while poor radiators, as smooth stones, and hard compact soils, 
remain almost dry. Clouds radiate back the heat received from the 
earth, so that cloudy nights are warm and dewless. If the tempera- 
ture sinks lower than 32°, the moisture is frozen, and becomes frost. 

340. Transmission and Destruction of Waves. — An opaque 
body destroys the luminous waves which fall upon it, while a 
transparent one permits them to glide through between the atoms 
without interference. But there are bodies which destroy some 
of the waves and allow others to pass. If a piece of red glass be 
placed between the prism and the spectrum, it stops the blue rays and 
transmits only the red, that is, it cuts down the more minute waves, 
and gives passage only to the larger. If blue glass be used, there 
is a reverse effect, the red waves being extinguished, and the blue 
alone transmitted. Both glasses are transparent, yet if placed 
together in the path of the rays, they are as opaque as a plate of 
iron ; each destroying what the other transmits. If a solution of 
permanganate of potash be used in the same way, it destroys the 
central waves of the spectrum, leaving the colors of the extremi- 
ties with a jet-black space between. 

341. Diathermancy. — This is also the case with the heat rays; 
they are of different kinds, like the colors of light, and are arrested 
and transmitted differently by different substances. Bodies which 
transmit heat freely are called diathermic ; those which arrest it, 
athermic. Rock salt (common salt in blocks) is the most perfect 

tion ? Absorption ? 339. How does dew depend upon radiation ? 340. What is 
the effect of red glass upon the decomposed waves ? Of blue ? Of both ? Of 
solution of permanganate of potash? 341. What are diathermic bodies % Ather- 
mic ? What are the properties of rock salt ? What has it been termed f What is 



144 



CHEMICAL PHYSICS. 



Fig. 136. 




Glass intercepting, and Rock Salt 
transmitting Heat. 



Fig. 137. 



-__„_ 



diathermic body, allowing all the heat rays — those from the sun 

and the hand to pass through with 
equal freedom. "What glass is to 
light, a plate of rock salt is to heat, 
and it has hence been aptly termed 
' the glass of heat/ This substance 
is therefore adapted to make prisms 
and lenses for the concentration and 
dispersion of dark heat. If a heated 
ball be placed between a plate of 
glass and one of rock salt, Fig. 136, 
and bits of phosphorus be laid upon stands beyond, though the 
salt be many times thicker than the glass, the 
dark heat passes freely through it, igniting the 
phosphorus, while it is quite arrested by the 
glass. In the same way a thin film of water 
will absorb the obscure heat, while liquid bisul- 
phide of carbon will transmit it. The relations 
of different substances to the radiants are repre- 
sented in the figures. The dotted arrows represent 
light ; the broken arrows, luminous heat, and the 
whole, or dark arrows, dark heat. If the plate 
of salt be smoked, it becomes opaque to light, 
but the heat still passes, while plates of trans- 
parent alum are opaque to obscure heat, and 
almost impervious to luminous heat. 

342. Sifting the Rays.— "We have said that 
the sunbeam is a bundle of heterogenous radia- 
tions, and that the prism spreads them out into 
a spectrum, thermal at one end, chemical at the 
other, and luminous in the centre. The same 
thing holds true of all sources of heat, luminous 
and obscure — they emit rays of different quali- 
ties. When the mixed rays from any source are 
passed through a plate, a certain portion of them 
is stopped, and another portion transmitted. 
Alum. But if the rays which have passed are made to 



Rock Salt. 
Fig. 138. 




Rock Salt Smoked. 
Fig. 139. 




Glass. 
Fig. 140. 




it fitted for ? What is shown by Fig. 136 ? How is rock salt related to the three 
radiations ? Smoked salt ? Glass ? Alum ? 342. When mixed rays pass through 
a substance, what is the effect ? How are they treated by a second similar plate ? 



THERMAL RADIATIONS. 



145 



fall upon a second similar plate, a much larger proportion will be 
transmitted than went through the first. The first plate sifted 
the ray, and the purified beam is better fitted to penetrate another 
similar plate. For example, a plate of alum stopped 91 per cent, 
of the heat rays, transmitting but 9 ; while a second alum plate 
transmitted 90 per cent, of the sifted rays, stopping but 10. 

343. This principle explains the fact that glass readily trans- 
mits solar heat, while it stops the heat from a red-hot cannon ball 
in large quantities. The rays of the sun in coming through the 
atmosphere are strained of the rays which would be stopped by 
glass, so that the altered beam passes our windows without loss. 

344. Absorption of Heat by Gases. — Some new and highly in- 
teresting results have been lately arrived at by Prof. Tyndall on 
the relations of radiant heat to gases. ■ The instrument he em- 
ployed consisted of a hollow tin cylinder, A B, Fig. 141, four feet 

Fig. 141. 




Tynd all's Apparatus for Gaseous Absorption. 

long and three inches in diameter. This is closed by caps contain- 
ing plates of the purest rock salt, which are screwed air tight 
upon its ends. The npper stopcock, C, connects the cylinder with 
an air pump by which it may be exhausted, and through the lower 
stopcock, C, air or any other gas may be admitted. The bent 
tube, U, contains fragments of pumice £tone, moistened with 
caustic potash, to absorb carbonic acid from the entering air ; and 

How do the two alum plates behave toward heat rays ? 343. Why does solar heat 
pass through glass, while that from a hot ball is stopped ? 344. Of what parts does 
Tyndall's instrument for investigating the relations of heat to gases consist? 

. 1 



146 CHEMICAL PHYSICS. 

U' contains pieces moistened with sulphuric acid, to absorb wa- 
tery vapor. At one end of the cylinder is placed the thermo- 
electric pile, with wires leading to the galvanometer, and at the 
other a cube, 0, filled with hot water ; while a tin screen, T, cuts 
off and admits the rays. 

345. Pure Air Diathermic. — If the cylinder be exhausted, and 
the screen withdrawn, heat enters, and traversing the vacuum, 
falls upon the pile without any loss ; none of it is absorbed on the 
way. If now the cock 0' be turned, and purified air be allowed to 
enter and fill the cylinder, there is no motion of the needle ; the 
air arrests none of the heat. ' Its atoms are apparently incompe- 
tent to shatter a single calorific wave : it is a practical vacuum as 
regards the rays of heat. 1 By a modification of the apparatus far 
more delicate, and after thousands of experiments, Prof. Tyndall 
found that dry air did exert a slight influence, deflecting the needle 
about one degree. Pure oxygen, hydrogen, and nitrogen behave 
like air, being almost neutral. 

346. Influence of Compound Gases. — If now compound gases 
are introduced into the cylinder, a remarkable effect appears. 
Olefiant gas, which is just as transparent as the air, arrests four 
fifths of the rays of heat. Pure, transparent ammonia is still 
more impenetrable, and arrests the heat as if the cylinder were 
filled with ink or pitch. The same effect is produced if only a 
small proportion of these gases is mingled with the air of the 
cylinder. To such, an extent is this true that it has been affirmed 
that the ammonia escaping from a bottle of hartshorn by a single 
act of inhalation, will exert a more potent action on radiant heat 
than the whole body of oxygen and nitrogen in the apartment. 
Some bits of paper were moistened and placed in tubes, so that 
the entering air carried with it a faint trace of odor. The effect 
was marvellous ; the aromatic vapor struck down the heat rays in 
crowds. The exhalation of bergamot arrested 44 times as much 
heat as the air ; that of lemon, 65 times ; an^of aniseed, 372 times. 
The absorbent power of the following gases is represented by the 
accompanying numbers : air, 1 ; oxygen, 1 ; nitrogen, 1 ; hydrogen, 
1 ; chlorine, 39; carbonic acid, 90; olefiant gas, 97; ammonia, 1,195. 

Explain their uses. 345. What is the effect when the cylinder is exhausted? 
When filled with pure air ? What did Tyndall ascertain with a more delicate 
instrument ? 346. What is the effect of olefiant gas ? Of ammonia ? What is the 
effect of a trace of ammonia? Of odors? 347. How are these effects explained* 



THEEMAL RADIATIONS. 147 

347.- The same explanation applies here as in the former case 
(337). We saw that in solids, single atoms, or the atoms of ele- 
ments, communicated their motion to the ether in a very imperfect 
manner, while compound groups produced more powerful effects. 
The same general fact now appears under totally different circum- 
stances. The atoms are no longer embarrassed by cohesion ; their 
movements are perfectly free, yet here again the elements oxygen, 
hydrogen, and nitrogen can only act upon the ether in the feeblest 
degree, while those of the compound gases which move in massive 
groups, are thrown into powerful vibration by the ethereal waves, 
and react upon them with corresponding energy. Prof. Tyndall 
remarks that oxygen, hydrogen, and nitrogen swing in the ether 
with hardly any loss of moving force; they bear the same relation 
to the compound gases that a smooth cylinder turning in water 
does to a paddle wiieel. 

348. Invisible rays thus become the means of sounding the 
atomic constitution of bodies. "While heat passes through com- 
mon oxygen without being intercepted, ozone, which is but an- 
other form of oxygen, arrests a large proportion of it like com- 
pound gases ; we therefore infer that its atoms are arranged in 
groups. Lampblack is an excellent radiator, and though an 
element, yet it is an allotropic condition of carbon, in which the 
atoms are probably grouped into complex molecules. 

349. Absorption of Heat by Aqueous Vapor. — These views 
are not only interesting in themselves, but of the utmost import- 
ance in the economy of nature. Aqueous vapor is highly opaque 
to the dark radiations. Where the atmospheric gases arrest one ray 
of obscure heat, the small proportion of watery vapor contained 
in the air strikes down sixty or seventy rays. Luminous solar 
heat penetrates the air, and falling upon the earth, is changed into 
obscure heat, which cannot be radiated back into space. The 
watery vapor is thus the ' barb ! of the atmosphere which pre- 
vents the escape of the heat, and thus maintains the temperature 
of the earth. It follows that if aqueous vapor were withdrawn 
from the air, the terrestrial heat would so quickly radiate away, 
that the earth would soon become uninhabitable ; the invisible 
watery element of the air is, therefore, the blanket which keeps 

To what are the different atoms in the ether compared ? 348. What work do the 
invisible rays perform? 349. What is the relation of aqueous vapor to obscure 
heat ? What is the effect of the aqueous vapor of the air ? What would be the 



148 CHEMICAL PHYSICS. 

the world warm. In all those localities where the atmosphere is 
dry, the nightly loss of radiant heat is great, so that even in the 
burning desert of Sahara there is nocturnal freezing. 

350. The sun's rays fall with intense power upon the snowy 
summits of high mountains, hut their ice never melts. Travellers 
testify that they have never suffered more from solar heat than 
when wading waist deep in the snows of Alpine mountains. But 
there is so little aqueous vapor in the higher atmospheric regions, 
that the heat escapes as fast as it is received, and thus high moun- 
tains are powerful condensers of the vapor which is brought by the 
air currents from below (574). c "Water in all its forms is so active 
a radiator, that it must play a most important part in this moun- 
tainous condensation. As vapor it pours its heat into space, 
and promotes condensation ; as liquid it pours its heat into space, 
and promotes congelation ; as snow it pours its heat into space, 
and thus converts the surfaces upon which it falls, into more pow- 
erful condensers than they would otherwise be. Of the numerous 
wonderful properties of water, not the least important is this 
extraordinary power of discharging the motion of heat upon the 
interstellar ether ! ' — (Tyndall.) 

§ IV. Interference of the Radiants. 

351. Interference of Waves — When two sets of waves upon 
water are made to flow together, two effects may take place. If 

the waves coincide, that is, if 
ridge corresponds to ridge and 
furrow to furrow, their height 
will be increased; but if the 
ridge of one corresponds with the 
trough of another, they will neu- 
tralize each other and the water 
become still. This is called in- 
terference. If one of the systems 
interim of wl^Ives. be retarded a whole wave length, 

or any number of whole wave 
lengths, there will still be no interference ; but if one be retard- 
effect of removing the aqueous vapor from the air ? 350. What is said of the heat 
upon high mountains ? Why does not the snow melt ? What is the effect of the 
radiation of water in all its forms ? 351. What is interference of water waves ? 




INTERFEEENCE OF THE RADIANTS. 



149 



ed half a wave length, one and a half, or two and a half, the 
hills will neutralize the hollows, and interference produce rest. 
Those effects may be shown by dropping two stones into still wa- 
ter near each other at the same moment. Two sets of concentric 
waves are formed, Fig. 142, and where their circles intersect each 
other and their crests coincide, the motion is heightened ; but where 
crest coincides with depression, their motions are mutually destroyed. 

352. Again, two stretched strings, or two tuning forks, may 
be so arranged, that, when simultaneously struck, they do not 
give forth a continuous sound ; but there is produced a series of 
sounds, alternating with a series of silences. For a moment the 
sound increases, then dies away and ceases, then again swells 
forth and declines, and so continues until the strings or the forks 
cease vibrating. During the pauses of silence, there is still rapid 
vibration, so it is certain that the sounds are extinguished by 
interference of their waves. 

353. Interference of Light.— If a beam of colored light be ad- 
mitted into a dark room by two pinholes made near each other 
in a thin sheet of metal, and be made to fall upon a screen at a 
short distance, the rays intersect 
each other, and a series of dark 
bands alternating with bright i\ 
stripes will be formed upon the e\ 
screen by interference of the ray 
from the two orifices. In Fig* 
143, a f represent the two pin- c 
holes, and c d eb & portion of the 
screen, c g being a line joining 
the two surfaces at right angles, 
and midway between the pin- 
holes. The rays, a c, f c, pass through equal paths ; their waves 
coincide at c, and, heightening each other's effect, a bright band 
is produced at c ; a d,fd will differ by the length of one wave, 
a e,fe by the length of two waves, and a 5, f h by the length 
of three waves; hence, there will be also bright bands at d, e, 
and o. But the rays from the two orifices, meeting at 1, 2, 3, dif- 
fer in length successively by half a wave, a wave and a half, and 



Fig. 143. 




Interference of Light. 



How may these effects be shown ? 352. How is interference of sounds manifested ? 
353. How may interference of light be produced ? Describe the experiment. 



150 



CHEMICAL PHYSICS. 



two waves and a half, and by thus interfering, extinguish each 
other and produce darkness. As the rays which meet at c are 
equal, it is obvious that all the other rays coming from a are 
lengthened, and all others coming from f are shortened. As this 
variation of length is gradual, there will be a gradual passage 
from the brightest light to complete darkness. This effect is ex- 
hibited by the shaded portion of the diagram. If the light from 
one aperture is intercepted, all the dark bands disappear. 

354. The multiplicity of these remarkable phenomena is proof 
of the extent to which wave motion is employed in nature. Thus 
we have seen that motion added to motion produces rest ; that 
sound added to sound produces silence ; that light added to light 
produces darkness ; and it has also been proved that heat added to 
heat produces cold, and chemical energy added to chemical energy 
produces inaction : in other words, there may be interference of 
the thermal and chemical radiations just as of light and sound 



i Y. Polarization of Light 





Light Polarized by Reflection. 



355. When light is reflected at 
certain angles from the surface of 
glass, water, marble, polished wood, 
&c, a portion of it undergoes a re- 
markable change. Although taking 
place all around us constantly, we do 
not perceive it, but it may be de- 
tected in various ways. Two plates 
of glass are blackened on one side so 
as to have but a single reflecting sur- 
face, and then placed as shown in 
Fig. 144, «, &, with their edges tow- 
ard the eye. A ray of common light 
falling upon a in the direction of the 
arrow is reflected, and, upon being 
thrown upon &, is again reflected. 
The ray is changed at #, as the al- 
tered structure of the line shows, but 
the effect is not apparent. If now 




354. What is the extent of this principle? 355. What happens when light is 
reflected at certain angles ? How is this change detected ? What is the effect of 



POLARIZATION OF LIGHT. 



151 



&, or the second plate, is turned a quarter round, its angle with 
the ray being preserved, reflection ceases, and the beam is extin- 
guished, Fig. 145. Turning it another quarter round, Fig. 146, 
the ray is again reflected ; and still another quarter revolution, 
Fig. 147, brings it on the opposite side to Fig. 145, and again 
extinguishes it. The beam may be reflected from surface to sur- 
face any number of times in the same plane ; but it has lost the 
ability of being reflected in planes at right angles to that plane, 
while common light may be reflected in all directions. It thus 
appears that the ray has acquired different properties on different 
sides. From its analogy to magnetic polarity, this change is called 
polarization, and the ray thus affected is said to be polarized. 
The angle at which the ray falls upon the polarizing surface is 
called the polarizing angle, and differs in different substances : for 
glass, it is 56° 45', while for water it is 53° 11'. 

356. Polarizing by Transmission. — Light transmitted obliquely 
through a bundle of thin glass plates, Fig. 
148, is polarized, and the same effect is also 
produced by its passage through certain crys- 
tals. A stone, called the tourmaline, is much 
used for polarizing purposes. A thin polished 
plate of it polarizes the light which passes 
through it, as in Fig. 149. If a second plate is 
placed parallel to the first, Fig. 150, the light 
passes through both ; but if the second plate 
is turned a quarter round, Fig. 151, the light 
is stopped. ' The rays of the meridian sun 
cannot pass through a pair of crossed tourmalines.' The plate 

Fig 149. Fig. 150. Fig. 151. 

Ml 



Fig. 148. 




Polarization- by Thin 
Plates. 





V 7 

Polarization by Tourmalines. 

polarizing the light is called a polarizer, that which tests or 
detects it after it is changed, is termed the analyzer. 



turning the plate b, fig. 144 ? How may the changed beam be reflected ? What has 
the ray acquired ? What is it called ? What is the polarizing angle ? 356. In what 
othei ways may light be polarized ? How do a pair of tourmalines affect the ray ? 



152 



CHEMICAL PHYSICS. 



357. The.wave theory affords a beautiful explanation of these 

phenomena. To recur 
to the illustration of 
the cord, it is obvious 
we can vibrate it up 
and down, horizontally, 
or in any direction 
transverse to its length, 
Fig. 152. In common light the undulations take place in all these 
directions at once. It has been suggested that common light may 
be represented by a round rod ; polarized light by a flat one. 
Supposing the round rod to image to us the common ray, the 




Vibration in Different Planes. 



Fig. 153. 



Fig. 154. 



Fig. 155. 





Fig. 156. 



Illustrations of Planes of Vibration. 

radii, Fig. 153, will exhibit the system of transverse vibrations 
taking place in all planes. But the effect is just the same if we 
regard the vibrations as taking place in tico planes only, at right 
angles to each other, as in Fig. 154. Now when common light is 
reflected in certain positions, which we have just noticed (355), 
one of its planes of vibration is destroyed, and 
the beam is polarized, its vibrations taking place 
all in one plane, Fig. 155. We can now easily 
understand the action of the tourmaline upon 
light. A plate of this crystal suppresses one 
of the planes of vibration, and, therefore, trans- 
mits a polarized ray. This will pass through a 
second plate if it is held in such a manner that 
its structure coincides with the motion ; but 
if it is turned so as to cross the waves, the ray is obstructed. A 
card which readily slips through a grate when its plane coincides 
with the bars, will be stopped if it is turned a quarter round, Fig. 156. 




Motion in a Single 
Plane. 



What is the polarizer? The analyzer? 357. How do the undulations take place 
in common light? What does figure 153 show? 154? What is the effect of the 
reflection, Fig. 155 ? How does the tourmaline polarize light ? How does the figure 



POLARIZATION OF LIGHT. 



153 



Fig. 157. 




Polarized Rays. 



Fig. 158. 




358. When a ray falls upon a transparent surface at a certain 
angle, its planes of vibration are resolved 
into two, one of which is reflected, and 
the other transmitted, Fig. 157; both are 
polarized, but one ray vibrates in one 
direction, and the other in another. 

359. Double Refraction.— Some sub- 
stances possess the singular property of 
splitting the ray which passes through 
them, producing an effect which is 
known as double refraction, Fig. 158. 
Iceland spar (a . carbonate of lime) and 
many crystals possess this power ; print- 
ed words or a candle flame seen through 
them appearing double Fig. 159. The 
effect is due to the molecular structure 
of the body. A cube of annealed glass, 
which usually gives only single refrac- 
tion, if unequally heated or subjected to 
pressure, divides the ray and manifests 
double refraction. The wave theory 
affirms that in double refraction the ray 
of common light has its two systems of 
undulations separated, and that the re- 
sulting rays must, therefore, be polarized, 
and at right angles to each other. Such 
is the fact; and if the beams be intercepted by a plate of tourma- 
line, one is stopped, and the other transmitted. 

360. Circular Polarization. — Light affected in the manner de- 
scribed is said to be plane polarized. If the end of the cord, Fig. 
152, be moved in a circle, circular waves will be formed, and so 
we have also circular polarization. The wave motion is similar 
to that which a strip of card would have if forced along two 
opposite grooves of a rifle barrel. Some substances rotate the ray 
in one direction, and some in another, while some rotate it more 
than others, but in each case the degree of rotation depends upon 



Double Refraction. 



Fig 159. 




Effect of Double Refraction. 



of the card and grate illustrate this? 358. How may the ray be separated? 
359. What is double refraction? How is it manifested? Upon what does it 
depend ? How does the wave theory explain it ? 360. How is circular polarization 
illustrated? How do bodies differ in relation to this property ? How is tho prop- 



154 CHEMICAL PHYSICS. 

the thickness of the medium. Solutions of sugar and most essen- 
tial oils turn the plane of polarization, and this property thus 
becomes a test of the nature of chemical substances, and of the 
strength of various solutions. Colored polarization is a branch of 
the subject having extreme interest, but it is too complex to be 
considered here. 

361. Uses of Polarized Light. — Not only is polarized light 
serviceable in the way just mentioned, but it has other applica- 
tions. The use of the tourmaline greatly diminishes the glare of 
reflected light, so that objects at the bottom of water, as rocks, 
shoals, or fish, may be more clearly seen ; and in the same way 
the pictures in a gallery may be better viewed. It also affords 
a method of determining whether the light from celestial bodies 
is direct or reflected. In a scientific point of view polarized light 
has great interest as a means of revealing the inner constitution 
of various substances which is not detected by common light. 

§ YI. Spectrum Analysis. 

362. Fraunhofer's Lines. — When the spectrum formed from a 
narrow line of solar light is viewed by a telescope, it is seen to be 
crossed by numerous dark lines of various breadths. They were 
discovered in 1802, by Dr. Wollaston, but excited little attention 
until they were rediscovered by Feaunhofer in 1815. He 
counted 590 from the red to the violet, and made a map of them, 
designating the most important by the letters of the alphabet (315). 
He further found that the lines did not vary in sunlight, examined 
at different times ; that the reflected light from the moon or from 
Yenus gives the same distribution of them as the sun, while the 
spectra of the fixed stars differ from those of the sun and from 
each other. From these considerations Feaunhofee drew the 
conclusion that the cause of the lines in the spectrum exists in 
the sun. 

363. The Spectroscope is an instrument for observing the lines 
of the spectrum. Fig. 160 represents it in its simplest form. 
Kays of light from the sun or lamp a, enter a narrow vertical slit 

in the tube &, and passing through the prism c 1 are refracted and 

» 

erty used? 361. What is the advantage of looking at objects through the tour- 
maline ? 362. What are Fraunhofer's lines ? What did Fraunhofer discover and 



SPECTRUM ANALYSIS. 



155 



Fig. 160. 



produce a spectrum. This is seen by looking into the spyglass d. 
The more perfect instruments have a third tube situated at e. 
which contains a scale 
for accurately measuring 
the spaces between the 
lines. To obtain a high 
dispersive power, hollow 
glass prisms filled with 
bisulphide of carbon are 
used, and several may be 
employed at once. ^Vhen 
in use the whole is cov- 
ered, to exclude the in- 
terfering light.* 

364. Spectra of the 
Elements. — It is common- 




The Spectroscope. 



ly known that different substances tinge the flame of burning bodies 
of various colors, as seen, for example, in the colored flames of fire- 
works ; but it has only lately been found that each element has, as 
it were, its c mark,' or autograph of light. Each one, when burned 
under suitable circumstances, emits a light, which, when passed 
through the prism, produces a spectrum so peculiar that it may 
serve to identify the element from which it proceeds. The inves- 
tigation of the spectra of the elements was lately undertaken by 
Kiechhoff and Buxsex, of Germany, and the interesting results 
open to us a new method of chemical analysis. 

365. How the Spectra are Produced. — To emit their peculiar 
light, bodies must be vaporized. An ordinary lamp or gas flame 
may produce the result, but it is most brilliant in the electric light. 
If a platinum wire be heated to whiteness, and its light passed 
through the prism, it gives a continuous spectrum ; but if it be con- 



* The Spectroscope of Frauxhofer was first used in this country by Dr. John 
W. Draper, of the University of Xew York, more than twenty-five years ago. 
He modified it in 1842 in such a manner as to cast the fixed lines upon the sensitive 
surface of daguerreotype plates, and published a map of the results, showing four 
great groups of these lines bej-ond the limit of the violet ray, and probably doub- 
ling the number of lines up to that time known. About the same time Prof. 
Draper published several papers on spectrum analysis, anticipating various things 
which have been lately brought forward as new (399). 



conclude? 353. What is the Spectroscope? Describe it. 364 How do different 
substances affect flames? What has been lately found? 365. In what condition 
do the elements require to be? Examples. What are the sodium lines? Doits 



156 CHEMICAL PHYSICS. 

verted into incandescent vapor by the electric current, its spec- 
trum becomes broken, and there is a series of brilliant lines sep- 
arated by varying intervals of darkness. If zinc be vaporized, it 
gives beautiful bands of red and blue ; if copper, they are of a 
brilliant green, while brass, which consists of both metals, gives 
both sets of lines at once. The metal sodium gives two very fine 
yellow lines situated close to each other, and so also does common 
salt and the other compounds of sodium. So amazingly delicate 
is this test that Bunsen claims to have detected the ^o\oTro,iroo °^ 
a grain of sodium. 

366. New Elements. — As Bunsen was examining the spectra 
of the alkalies, he observed some bright lines which did not belong 
to them, and which led him to suspect the presence of a new 
metal associated with these bodies. Further investigation proved 
the truth of his conjecture. On evaporating 40 tons of a certain 
mineral water, he obtained 105 grains of the chloride of a metal 
which gives two splendid violet lines in the spectrum, and which 
he called Ccesium, from cmsius, bluish gray. He obtained also 135 
grains of the chloride of another metal, which gave two bright 
red lines, and which he named Rubidium, from rubidus, dark red. 
Mr. Ceookes has since discovered a new metal resembling lead, 
which is distinguished by a spectral band of bright green, and has 
hence been called Thallium, 

367. Coincidence of Bright and Dark Lines. — In order to map 
the positions of the bright lines of various metals, Kikchhoff 
employed the dark lines of the solar spectrum as his guide. Upon 
placing one spectrum over the other, he was astonished to find 
that whole systems of lines in the two spectra were coincident ; 
the bright lines of potassium, sodium, chromium, magnesium, 
iron, and nickel, exactly corresponding with the same number of 
dark solar lines. The spectrum of vaporized iron gave about 
60 bright lines, which precisely coincide in grouping, breadth, and 
separation with the same number of dark lines in the spectrum of 
the sun. This could be no accidental result. Kikchhoff calcu- 
lated that the chances are more than 1,000,000,000,000,000,000 
to 1 that they are both due to the same cause, and that, therefore, 

compounds give it ? What does Bunsen claim ? 366. What le>i Bunsen to suspect 
the existence of new metals ? How did he proceed ? "What did he discover ? 
367. What discovery did Kirchhoff make? What did he find concerning tho 
iron lines? What probability did Kirchhoff work out? 368. When light is 



SPECTRUM ANALYSIS. 



157 



there must be incandescent iron vapor in the atmosphere of the 

sun. 

368. Dark Lines Produced by Absorption. — When light is 
transmitted through certain vapors, and then passed through the 
prism, the spectra exhibit dark lines which vary in the different 
cases. Fig. 161, No. 1, shows the dark lines of the pure solar 

Fig. 161. 




Absorption of Light by Gate.-?. 



spectrum ; No. 2, the influence of vapor of bromine upon the ray, 
and No. 3, that of the red fumes of nitrous, acid. The wave 
theory explains these results. We have seen that gases and vapors 
destroy some of the rays of heat, and let others pass. The same 
thing occurs here ; the vibrating atoms of the vapors strike down 
certain classes of the waves — they are absorbed, and hence the 
dark lines in the spectrum are lines of absorption. 

369. What Rays are Absorbed ? — This question carries us one 
step further in this interesting inquiry. We have learned in the 
case of heat that the good radiator is the good absorber ; that is, 
that the same vibrations which emit a train of waves will also 
arrest them. The same thing is true of colors. c The atoms 
which vibrate red light will stop red light ; those which oscillate 
green, will stop green, and so of the rest.' 

370. This remarkable fact is proved by throwing the ray of an 
electric lamp through a flame containing metallic vapor. The 
vapor will arrest the same kind of rays that it gives out, and its 
spectrum will be reversed, dark lines replacing the bright ones. 
For example, if an electric light is made to shine through the 
sodium flame, the two yellow lines of its spectrum are changed to 
dark lines. The rays that the sodium emits are also arrested. 



transmitted through vapors, what is the effect ? How is this explained? 369. What 
principle prevails here which, we have learned before ? 370. How is this proved ? If 
an electric light is passed through the sodium flame, what results ? Are the dark lines 



158 CHEMICAL PHYSICS. 

The dark lines thus produced, are, however, only relatively dark ; 
the sodium continues to emit its bright lines, but the light inter- 
cepted is so much more brilliant than that emitted, that the lines 
appear as dark spaces in comparison with the rest of the spec- 
trum. The dark lines are thus lines of absorption. 

371. Cause of the Dark Solar Lines.— These views afford an 
explanation of the cause of the dark solar lines. Astronomy 
teaches that the sun consists of two parts ; a central orb, or 
nucleus, of intense brightness, surrounded by a luminous atmo- 
sphere (photosphere), so that there are two sources of solar light. 
If the light from the central orb could be intercepted, we should 
receive only rays from the photosphere, and its spectrum would 
give us all the dark lines of Feaunhofek as bright lines, owing to 
the chemical substances which exist in it as vapor. But as the 
rays of the far brighter nucleus pass through the photosphere, it 
stops all those which it can itself emit, and thus gives us the dark 
lines of the solar spectrum as lines of absorption. 

§ VII. Chemistry of Light. 

Fig- *62 . 372. It was known to the alchemists that light 

exerts a chemical effect upon various bodies, as, for 
example, blackening the salts of silver. Sciieele, a 
German chemist of the last century, proved that this 
effect is most intense in the violet region of the spec- 
trum ; and Bitter, of Geneva, in 1801, discovered the 
separate existence of dark rays more refrangible than 
the violet which produce chemical changes. 

373. The Chemical Spectrum. — When a sheet of 
white paper is washed over with a solution of nitrate 
of silver, and the prismatic spectrum is made to fall 
upon it, a change occurs; the paper blackens. The 
outline of the darkened space is represented in Fig. 
162. This third spectrum also exhibits a break or 

Chemical interruption like that of heat. The dark band is the 
point of no chemical action, and occurs in the yellow 

space. The radiations which produce these effects have been 

. . _ ^ 

absolutely dark ? 371. What does astronomy teach concerning the sun ? If the solar 
nucleus were abolished, what -would be the result ? How are the dark solar lines pro- 
duced ? 372. What facts concerning the effects of light were known to the alchemists ? 
To Scheele ? To Hitter ? 373. How is the chemical spectrum formed ? -What is 



CHEMISTRY OF LIGHT. 



159 



Fig. 163. 



termed the actinic rays, or actinism, a word which signifies liter- 
ally ray 'power. They are, however, more commonly known as 
the chemical rays. 

374. Thus the sunbeam is a line of forces through which the 
sun has a threefold control over terrestrial matter. It transmits 
an expansive energy which controls the magnitude and 
forms of bodies ; a luminous influence which impresses 
the nerve of the animal eye, and a chemical force which 
governs affinity. Fig. 163 represents the position and 
intensities of the three forces in the prismatic spectrum. 
The course of the curve a defines the intensity and ex- 
tent of the heat ; &, of the light ; and c, of the chemical 
force. The agency of light in the production of organic 
matter will he considered in Physiological Chemistry. 

375. Analogies of the Chemical Force with Light. — 
That the chemical element of the ray is of the same 
nature as light, is proved by the completeness of its 
analogies with it. It moves in straight lines with the 
same velocity, and is diffused, reflected, refracted, double- 
refracted, and polarized like light. It also undergoes 
interference, and gives the lines of absorption ; and as 
there are different kinds of light, so there are also differ- 
ent kinds or qualities of chemical force which take effect 
upon different classes of compounds and correspond to colors. 
We are thus brought to consider chemical action as a motion of 
atoms, and the chemical changes of the spectrum as produced by 
ethereal waves. 

376. How Light Produces Chemical Change. — As the increase 
of vibration throws atoms beyond the sphere of cohesion, so it 
also throws them beyond the sphere of affinity, producing decom- 
position. In cohesion, the atoms are alike, and vibrate alike ; in 
affinity, they are totally unlike, and vibrate at different rates. Ele- 
ments, having the highest and lowest atomic numbers, as hydro- 
gen and the noble metals, do not combine at all ; their motions 
being se different that they cannot keep together. Others move 
at such rates that they unite only feebly, and the slightest increase 
of atomic motion separates them. A stream of waves, falling upon 



The three 
Spectra. 



said of it ? 374. "WTiat are the effects of the sunbeam ? How are the three spectra 
situated ? 375. In what respects is the chemical element of the ray analogous to light 1 
376. Upon what does affinity depend ? "What substances will not combine ? How 



160 CHEMICAL PHYSICS. 

a group of unequally vibrating atoms, acts upon them unequally, 
and thus tends to increase the diversity of their motion. When the 
successive wave strokes are so timed to the motion of an atom as 
to increase its oscillations, the effect accumulates, the atom is de- 
tached and thrown within reach of new affinities. In this manner 
one compound is destroyed and another formed. 

377. Measurement of the Force. — If hydrogen and chlorine 
gases are mingled together in the dark, their rates of vibration are 
so different that they do not unite. If brought into diffused day- 
light, they gradually combine ; if into the sunshine, they combine 
explosively. This change is effected by the chemical rays which 
are absorbed ; that is, the ethereal motions are taken up by the 
gaseous atoms which are thus brought into combining relations. 
The amount of condensation which occurs has been employed as 
a measure of the force in action (616). 

378. Photography. — This beautiful art is a result of the chem- 
ical action of light. A metallic, glass, or paper surface is coated 
with some chemical substance which is changed by light, and, 
therefore, said to be sensitive. The prepared tablet is then placed 
in a camera obscura, a darkened chamber, with lenses on one side, 
by which the images of external objects are formed within. These 
are made to fall upon the sensitive surface, when a change takes 
place, its intensity corresponding to the intensity of the light. 
The brightest points are most changed, the darkest least, and those 
between intermediately, so that the lights and shadows pass into 
each other gradually. The processes for making pictures will be 
referred to after treating of the chemical substances used (870). 

379. The Picture Formed by a Dark Force. — Photography or 

light-drawing is an erroneous 
term, as it is not the light which 
acts, but the dark radiations 
with which it is associated. 
Hence, as the chemical rays are 
a & c ™ more refrangible than tj^e lumin- 

a, Heat ; 5, Light ; c. Chemical Force. , , , ' -. , . , 

ous, and are gathered to a point 
sooner, Fig. 164, the accurate operator makes allowance, and 
advances the prepared plate slightly forward from the luminous 

does the radiation produce decomposition? 377. How is the chemical force meas- 
ured ? 378. How are photographic impressions produced ? How are the lights and 
shadows related? 379. Why is photography an erroneous term? How may a 



CHEMISTEY OF LIGHT. 161 

to the chemical focus. By a proper arrangement, the chemical rays 
of the spectrum which are beyond the region of light, may be thrown 
into a darkened apartment against an object, and, being reflected 
upon a sensitive surface, will produce a picture in total darkness. 

380. By reference to the curves, Fig. 163, it will be seen that 
light and the chemical force are antagonistic — where the former 
is strongest, the latter is weakest. As we approach the equator, 
therefore, the light becomes so brilliant as to interfere with the 
process, and make it difficult to take pictures. 

381. Instantaneous Impressions.— A train of cars at high speed, 
if seen at night by a lightning flash, seems standing at rest : so a 
wheel revolving many hundred times a second in a dark room, if 
illuminated by an electric spark, appears to stand still — so incredi- 
bly brief is the duration of the light. Mr. Fox Talbot placed 
upon a wheel a printed bill so as to produce its image in a camera. 
He then darkened the room, placed a highly sensitive plate in the 
camera, set the wheel to revolving at the rate of 200 revolutions 
per second, and illuminated the apparatus by an electric spark. 
A definite and legible impression of the Mil was obtained. While 
the light acted, the wheel could not have moved through the y^ 
of a revolution, that is, the picture must have been taken in less 
than the ao.ioo °f a second — one of the most astonishing results 
in the whole range of science. 

382. Chemistry of the Stars. — According to the faith of the 
old alchemists, the earthly elements were ruled by the magical 
influence of the stars. It was a prophetic dream, and has been 
fulfilled in the consummate researches of modern science, which 
has given us a true celestial chemistry. The spectrum of the stars 
has its bands of absorption, and Mr. Buthekfokd, of New York, 
has discovered a coincidence between several of the dark lines of 
Arcturus and those of the sun — these lines being possible indica- 
tions of the chemical conditions of their sources. The light of the 
stars also contains a positive chemical energy ; they are photo- 
graphed by the astronomer. He prepares his chemical map, and 
they telegraph across the universe, registering upon it their exact 
places. Though situated so profoundly in the depths of space 

picture be produced in darkness ? 380. How are the chemical and luminous forces 
related? 381. Under what circumstances do moving bodies appear at rest? De- 
scribe Talbot's experiment? 382. What dream of the alchemists has science 
realized ? What is the relation of the stars to earthly matter ? What is their 



162 CHEMICAL PHYSICS. 

that it may require thousands of years for their impulses to reach 
us, the stars, nevertheless, exert a control over the conditions of 
earthly matter, producing decomposition and regrouping chemical 
atoms. In fact light itself is a physiological force effecting nerve 
changes — a kind of vital photography in which the pictures are 
sensations, and translate the outer world into the sphere of con- 
sciousness. Thus the radiations of the heavenly bodies are the 
mysterious links which bind the vast universe to our world of 
matter, life, and mind. 

383. Phosphorescence is a property possessed by various bodies 
of emitting a faint light at ordinary or low temperatures, and is so 
named from phosphorus, which exhibits it in a remarkable degree. 
Phosphorescence is manifested by certain insects, as the firefly and 
glowworm, by several species of plants, by various animal and 
vegetable substances in a state of decay, and by exposure of many 
substances to sources of light. If a sheet of paper or the hand be 
placed in sunshine for a short time, and then withdrawn into dark- 
ness, they will continue to glow for a few seconds, while other 
bodies, as the diamond and chlorophane, after exposure, remain 
for a long time luminous. The cause of these phenomena is not 
fully understood. It is maintained by some that there is a fourth 
class of rays in the sunbeam which have the power of exciting 
phosphorescence, and are hence called phosphor ogenic rays. The 
diamond will not glow if protected from the sun by the thinnest 
glass ; therefore, glass is assumed to be opaque to these rays ; on 
the other hand, smoked quartz, which arrests the light, permits 
this effect to pass. 

384. Persistence of Impressions. —Slight and evanescent as 
these effects may seem, they nevertheless cling to matter with 
surprising persistence. If we cover a board with powdered sul- 
phide of calcium (made adherent by a previous coating of gum 
arabic), lay a key upon it, and expose it for a few minutes to sun- 
light ; on bringing it into a dark room, and removing the key, a 
dark, well-defined image of it is seen on a white ground. The sur- 
rounding phosphorescent glow gradually diminishes, and the image 
disappears. Now, place a pencil upon the surface, and expose it 
again, and when the image vanishes, repeat the exposure a third 



physiological significance ? 383. What is phosphorescence ? How may it be man- 
ifested ? What is said of its cause ? 384. Are these effects persistent ? By what 



CHEMISTRY OF LIGHT. 163 

time with a ring. When all traces of the last image are gone, heat 
the board, and the images will reappear in reverse order — first, the 
ring, then the pencil, then the key; and they have been thus evoked 
weeks and months after they were formed. 

385. Universal Impressibility of Matter. — It was at first sup- 
posed that light affected only a few peculiar substances, but the 
progress of chemistry has shown that the sunbeam can hardly 
fall upon a surface of any kind without producing a molecular 
change and leaving a lasting impression. 

386. If an engraving which has been for some time in the 
dark is one half exposed to the sunlight, the other being kept per- 
fectly covered, and then removed to a dark coom and placed in 
close contact with a sheet of prepared photographic paper, the 
portion which was exposed to light is reproduced on the sensitive 
paper, while the protected part produces no effect. Again, an en- 
graving, charged with sunshine and placed in the dark a quarter of 
an inch distant from a surface of sensitive paper, was reproduced 
without contact and by radiation of dark force. 

387. Moser's Images.— It would, moreover, seem that oae 
object can hardly touch or approach another without impress- 
ing a change upon it, which is more or less lasting. If we 
lay a wafer or small coin upon a piece of clean cold glass, or 
polished metal, and breathe upon the surface, upon tossing off 
the object, after the moisture has evaporated, not a trace of it re- 
mains. But if we breathe upon it again, a spectral image of the 
coin or wafer comes forth, which, as it fades away, may be again 
and again recalled by a breath, even months afterward. These 
images were discovered by M. Moser and Dr. Draper about the 
same time. Objects also impress each other without contact. 
Engineers have noticed that the near parts of machinery visibly 
impressed each other. By exposure over night, a very distinct 
image of the grain of wood has been obtained, when placed more 
than half an inch from the receiving surface. 

remarkable experiment is this shown ? 385. "What is said of the extent of these 
effects ? 386. What experiments may be made with engravings ? 387. Describe 
the experiment with the wafer. Who are its discoverers ? / 




164 CHEMICAL PHYSICS. 

CH^PTEE VI. 

MUTUAL RELATIONS OF THE FORCES. 

§ I. Connection of Polarities. 

388. Ideas of Force Progressive. — With the progress of sci- 
ence ideas of force are refined. It was so in Astronomy. The 
earliest notion of the cause of celestial motions was that of solid 
crystalline spheres by which the heavenly bodies were supported 
and carried round in their courses. This idea was replaced by 
that of the more flexible mechanism of epicycles. To this suc- 
ceeded Descaetes's more refined hypothesis of vortices. He repre- 
sented the planets and satellites as owing their motions to oceans 
of fluid diffused through the celestial spaces, which constantly 
whirled around in vortices, and bore along the heavenly bodies. 
Newton first cleared away these material devices, and substituted 
the idea of an immaterial force acting according to mathematically 
demonstrated laws. 

389. So also with heat, light, electricity, and affinity; they 
have passed through their material stage, and are now to be 
regarded as kindred and convertible modes of motion. The pres- 
ent chapter will recapitulate some points already noticed, and still 
further illustrate the later and larger views of the relations of 
forces. 

390. Rise of the Idea of Polarity. — Newton fixed the atten- 
tion of the world upon the play of central attractions through the 
universe. This idea so completely occupied the thought of the 
last century that men fancied the entire mechanism of nature — 
molecules as well as masses — was moved by central attractions. 
But about the beginning of the present century it began to be 
perceived that another and widely different mode of force plays 
an important part in her scheme. This is the principle of polar- 
ity. We have seen it working in various forms, but in them all 
we discover the common characteristics of opposite powers or prop- 

388. What has been the progress of ideas of force in astronomy ? 389. Has 
this principle been carried farther? 390. What was the influence of Newton 
in regard to forces ? What principle has been lately brought forward ? What 



CONNECTION OF POLAKITTES. 165 

erties in opposite directions. A very intimate and interesting 
. series of relationships may be traced among these polarities. 

391. Magnetic and Electric Polarities.— In the case of mag- 
netic and electric forces, it was suspected, long before Oeested 
made the discovery, that they were in some way intimately re- 
lated. This connection, however, turned out to be more constant 
and extensive than had been imagined. A magnetic needle, when 
placed near a galvanic wire, is jerked out of its position and 
turned across the current. A galvanic wire is made to revolve 
round a magnet, and a magnet round a galvanic wire. Artificial 
magnets are made of coils of galvanic wire ; and, finally, the gal- 
vanic spark itself is obtained from the magnet. "We cannot escape 
the conviction that whatever be the nature of these polarities, 
they are due to the same cause. 

392. Electric and Chemical Polarities. — In chemical pro- 
cesses, opposites (acids and bases for example) are attracted to- 
gether and neutralize each other. It is true we do not here have 
1 unlike poles attracting, and like poles repelling,' as in magnetism 
and electricity, but these are only special modes in which the 
principle of polarity is manifested, and are not essential to it. 
The conception of opposite properties and mutual neutralization 
involves the idea, and makes the chemical a true polar force. 
Fakaday teaches that chemical combination and decomposition 
must always be regarded as taking place in virtue of equal and 
opposite forces, by which the particles are united or separated; 
and he has used this very case to teach us that, in the general 
idea of polarity, we must get rid of the notion of attracting poles. 
We have seen chemical action produce electric currents, and elec- 
tric currents chemical action. These polarities are believed to be 
but different phases of the same principle. 

393. Chemical and Crystalline Polarities. — It is evident there 
is a very close connection between chemical affinity and the 
attraction which arranges together the particles of a crystal. 
Chemical affinity takes the elements out of solution, and places 
them in a fixed polar arrangement (106). The force which draws 

is the essence of polarity ? 391. "What was long suspected concerning the 
magnetic and electric forces? Why are they now considered to be due to 
the same cause ? 392. How is the chemical shown to he a polar force ? What 
is the teaching of Faraday concerning it ? What relation exists between chemical 
attraction and electric currents ? 393. What is said of chemical affinity and crys- 



166 CHEMICAL PHYSICS. 

the particles together, and that which places them in a crystalline 
order, are evidently one. 

394. Crystalline and Optical Polarity. — Here also is a most 
intimate and beautiful connection. "We have seen that crystals 
are used for polarizing light, but this power depends upon the 
axis of the crystal ; that is, the direction of the polarities of the 
crystalline particles. It has also been observed that the action of 
heat and electricity upon bodies is influenced by the polarity of 
their atoms (267). 

395. Magnetism and Light.— A beautiful illustration of these 
connections was discovered by Faraday, in 1845. A piece of 

flint glass, A, Fig. 165, is placed between 
Fig. 165. the poleg ^ g f a powerful electro- 

magnet, and a ray of light, polarized in a 
vertical plane by reflection from a piece of 
blackened glass, passes through the glass 
A, and is viewed through a piece of Ice- 
land spar (NicoVs prism). So long as the 
bars N" and S are not magnetic, the ray 
is passed or stopped as usual by revolving 

Magnetism and Light. ,, . Ti? ., , , ^ ,, , 

the prism. If now it be turned, so that 
the ray is darkened, and the wires C and Z are connected with the 
battery, the bar is made magnetic, it affects the glass, and the ray 
instantly becomes visible. A chain of four polarities, electric, 
magnetic, luminous, and crystalline, is called into action in* pro- 
ducing this remarkable effect. If we add the organic polarity of 
the nerve of vision, we have a fifth link of the polar series. 

396. Optical and Thermal Polarities. — It only remains now 
to state that heat is capable of being polarized like light to com- 
plete the mysterious chain of influences which shows that there is 
some common principle of action among these forces, and a deeper 
unity of cause than was formerly suspected. 

§ II. Connection of the Radicmt Forces. 

397. The intimate connection of the radiant forces has been 
before referred to, but requires further illustration. Fig. 166 

tallization ? 394. Upon what does the power of the crystal to polarize light depend ? 
395. What is the connection between magnetism and light ? Describe the experi- 
ment, Fig. 165. What polarities are here called into play ? 396. What is said of 




CONNECTION OF THE RADIANT FORCES. 



167 




represents the contents of a luminous beam a, spread out by the 
prism from b to t. The heating effects begin at 6, and extend 
through the space em- Fig 16g 

braced by the thermal r 

bracket, varying in in- 
tensity and quality at chem- 
each point. The differ- Force, 
ences among the ther- 
mal rays so much re- 
semble those of color, The f- 

' mal 

that Melloni designa- Force, 
ted this phenomenon as 
the ' ideal coloration 
of heat.' The middle ' 6 

bracket of the diagram Distribution of the Forces of the Spectrum, 
gives us a scale of radiations which produces the world of colors, 
while the chemical bracket comprehends a wide range of chemical 
intensities which take effect upon different compounds in the dif- 
ferent spaces. The continuous lines indicate heat rays ; the broken 
lines, chemical rays ; and the dotted lines, luminous rays. 

398. Identity of Heat and light Motions.— It has been said 
that all these radiations obey precisely the same laws of movement ; 
but the analogies of heat with light are carried much farther than 
has yet been stated. Eot only has the interference of heat 
been proved, but no change or manifestation can be impressed 
upon light that does not affect the associated heat in the same 
manner and degree. The heat ray undergoes double refraction 
by Iceland spar, and the two separated beams are polarized in 
planes at right angles to each other (359). The phenomenon of the 
magnetic rotary 'polarization of heat has also been observed. 
These facts show beyond question that heat cannot be a material 
substance, but is a mode of motion of the same nature as light. 

399. Dr. Draper's Experiment.— Still more conclusive on this 
point are the beautiful experiments of Prof. Deapee. He sub- 
jected various substances, under suitable circumstances for ob- 
servation, to the action of heat, and found the order of effects 

heat? What does this show? 397. What does Fig. 166 represent? How does 
Melloni regard the differences among the heat rays ? What does the highest 
bracket in Fig. 166 include ? 398. In what additional respects does heat resemble 
light? 399. What is observed at the commencement of Draper's experiment? 



168 CHEMICAL PHYSICS. 

strictly dependent upon the energy of the combustion, or source 
of heat. At the commencement of the action, as the body begins 
to be heated, the rays emitted are of the lowest refrangibility, 
being but slightly refracted by a prism of rock salt. As the 
molecular action of combustion increases, the refrangibility and 
intensity of the heat rays increase. At about 1000°, the emitted 
rays become so energetic that they begin to act upon the eye, pro- 
ducing the sensation of a dull red light, and this effect takes place 
at the same thermometric degree with all solids. As the temper- 
ature ascends, the colors of the spectrum appear in the order of their 
refrangibility ; red, orange, yellow, green, blue, indigo, and violet. 
At 2130° all the colors are produced, and from their commixture 
the substance appears white hot; actinic effects then appear in full 
intensity. As the body cools, the order of effects is reversed, and 
the colors disappear successively, from the violet to the red. 

400. How Heat and Light Differ. — The foregoing experiment 
proves that all the diversified effects of the spectrum are due to 
one energy. Heat and light are not the same thing, but they have 
Tme cause. Heat rays differ from light rays simply as one color 
differs from another. It is well known that the selfsame force 
produces widely different effects according as it acts upon different 
media. The same electric current, if sent through a thin wire, pro- 
duces heat ; if sent round a piece of iron, produces magnetism; 
and if through a conducting liquid, chemical decomposition. So, 
the same agent, acting upon different organs of the body, affects 
our consciousness differently ; — falling upon the nerves of feeling, 
it excites the sensation of heat ; and upon the nerves of seeing, the 
sensation of sight. 

401. Fluorescence — Dark Rays changed to Light. — The con- 
version of one radiant force into another, and the influence of the 
body upon which it acts, are strikingly exemplified by a discovery 
of Prof. Stokes. He filled a glass tube with a solution of sulphate 
of quinine, and then moved it through the spectrum, entering at 
the red ray. No unusual effect was produced till it passed the 
extremity of the violet, and entered the region of the chemical 
rays, when ' a ghostly gleam of pale blue light shot across the 

As the action becomes more intense, what follows ? What results when the body 
cools ? 400. What does this experiment prove ? How does heat differ from light ? 
How does the electric current produce different effects ? How may the same agent 
produce different sensations? 401. Describe the experiment of Prof. Stokes. 



CONSERVATION OP FORCE. 169 

tube. 7 The dark chemical force was changed to light by the 
quinine solution. Thus the same force acting upon one surface, 
produces one effect, and upon another, an opposite one. Various 
substances give rise to this result, as a decoction of horse chestnuts, 
glass stSined with oxide of uranium, &c. They have the property 
of receiving rays of one refrangibility, and emitting them at a 
lower one ; and, as the colors of the spectrum are similarly low- 
ered in the scale of refrangibility by these substances, the phe- 
nomenon was first known as the degradation of light. The term 
fluorescence is now applied to it, because it is very strongly mani- 
fested by a body known z&fluor spar. 

§ III. Conservation of Force. 

402. We have referred to the great truth that force, like mat- 
ter, is persistent and indestructible : its changes are but mutations 
from form to form ; an impulse of force can no more be created 
or destroyed than a particle of matter. This principle is known 
as the conservation of force, and is characterized by Dr. Faraday 
as ' the highest law in physical science which our faculties permit 
us to perceive.' The phrase correlation of forces has been used 
to indicate their mutual convertibility, but both forms of expres- 
sion imply the same great principle. 

403. History.— This is but another case, of which the history 
of science furnishes so many, where a great discovery belongs 
rather to an epoch than to an individual. In the growth of scien- 
tific thought, the time had come for the evolution of this prin- 
ciple, and accordingly several master minds seized upon it inde- 
pendently about the same time. Among these are MayePw and 
Helmholtz, of Germany, Oolding, of Denmark, and Joule, Grove, 
and Faeaday, of England. These discoverers announced their 
results between 1840 and 1850; they became generally known 
during the next ten years, and are now established as comprehen- 
sive and guiding principles of science. 

404. Origin of the Idea of Perpetual Motion. — To common 

What was the effect ? What other substances manifest this property ? How were 
the phenomena first known ? What are they termed now, and why ? 402. What 
is the conservation of force ? How is it characterized by Faraday ? What is the 
correlation of forces ? 403. What is said concerning its discovery ? To whom does 
it belong? What was done between 1840 and 1850? Between 1850 and 1860? 
8 



170 CHEMICAL PHYSICS. 

observation, when a moving body comes to rest, its force is anni- 
hilated, and this has been generally believed. The notion that 
force might thus pass out of existence — from something to nothing 
naturally led to the corresponding idea that it might be created, 
or comQfrom nothing. These loose conceptions of force gave rise 
to the fallacy of a perpetual motion — a machine that could go on 
forever., producing its own power, with no external supply of 
force. 

405. Persistence of Mechanical Force. — This error was first 
detected in mechanics. It was found that machines do not create 
force, but only communicate, distribute, and apply that which is im- 
parted to them. In all cases, the force expended is exactly measured 
by the resistance overcome. In the case of water power, to lift a 
hammer of 100 pounds, 1 foot high, at least 100 pounds of water 
must fall through 1 foot ; or, what is the same thing, 200 pounds 
must fall through ^ a foot, or 50 pounds through 2 feet. If a 
hammer weighing 1,000 lbs. is employed, with the same driving force 
it will either be raised to only Jo the height, or tenfold the time 
will be required to raise it to the same height. Thus, in mechan- 
ics, a certain amount of power or change acting as cause produces 
an exactly equal amount of change as effect. 

406. Convertibility of the Forces. — Now what occurs here 
is but the consequence of a universal law which applies to all 
kinds of physical energy. The preceding pages have afforded 
numerous illustrations of the production of one force by another. 
Heat, we have seen, excites electricity, and through that magnet- 
ism, chemical action, and light. Or, if we start with magnetism, 
this may give rise to electricity, and this again to heat, chemical 
action, and light. So, chemical action produces heat, light, and 
electricity ; and it has been also found that a mere line of decom- 
posing particles manifests a direct magnetic influence. That elec- 
tricity sets the whole series in action is strikingly exemplified by 
electrifying the sulphuret of calcium, or some similar substance. . 
At the instant of electrization, it becomes magnetic; is heated, 
and, if the electricity be sufficiently intense, it becomes luminous ; 
that is, light is produced. It expands, therefore there is motion ; 
and is decomposed — hence there is chemical action. 

404. What is the origin of the idea of perpetual motion ? 405. What was found in 
regard to machines? What is the relation between lifting a hammer and the 
descent of water ? 406. What forces may be produced by heat ? What examples 




CONSERVATION OF FORCE. Ill 

407. ' Friction against Space/ — A new and remarkable illus- 
tration of the effect of resistance to motion in producing heat has 
been lately discovered. If a blade of copper or any conductor 
be moved backward and forward between the poles of an active 
and powerful electro- Fig 167 

magnet, although it 
touches nothing, it 
will be resisted as 
if it were sawing 
through cheese, and 
become hot. A cop- 
per cylinder filled Magnetism resisting Motion. 

with alloy, and mounted between the poles, P P, Fig. 167, seems 
grasped by an invisible hand. If rapidly spun around by the 
string s s, attached to a wheel, it will grow hot, and, in three 
minutes, the alloy will be melted ; indeed the copper cylinder 
may be made red hot. The heat produced is in precise proportion 
to the force expended in increasing the resistance. 

408. Grove's Esperiment. — In a very beautiful experiment, 
Mr. Grove produced the whole circle of forces by using light as the 
exciter. He inclosed a sensitive daguerreotype plate in a box 
having a glass front with a shutter over it. Between this glass 
and' the plate was a gridiron of silver wire. The daguerreotype 
plate was connected with one extremity of a galvanometer coil, 
and the wire gridiron with a Beegtjet's thermometer ; * this and 
the galvanometer being also connected, so as to form a complete 
circuit. When the shutter was raised and a beam of light admit- 
ted, chemical action was produced in the plate ; electricity in the 
wires ; heat in BREGrET's helix ; magnetism in the coil, and 
motion in the galvanometer needles. 

409. Forces Convertible in Definite Quantities. — These trans- 
mutations take place in definite quantities. It is well understood 



* Breguft's thermometer consists of a vertical helix compounded of two rib- 
bons of different metals. The slightest amount of heat, by causing unequal expan- 
sion of the two metals (238), uncoils the spiral and produces motion, which is 
indicated by a horizontal needle passing over a scale. 



are given of forces producing each other ? What is the effect of electrifying the 
sulphuret of calcium? 407. What is the effect of sawing a piece of copper back 
and forth between the poles of an electro-magnet? Describe the experiment, 
Fig. 167. 408. What is shown by Grove's experiment? 409. What is the 



172 CHEMICAL PHYSICS. 

that a certain amount of fuel is necessary to perform a given 
amount of work with a steam engine. This means strictly that a 
definite quantity of the chemical action of combustion gives rise 
to a fixed quantity of heat, and this to a determinate quantity of 
mechanical effect. Dr. Faraday made the important discovery 
of the definite chemical effect of the voltaic current. He found 
that an equivalent of an element consumed in a battery gives 
rise to a definite quantity of electricity, which will produce 
exactly an equivalent of chemical decomposition. For example, 
the consumption of 32 grains of zinc in the battery, excites a 
current which will set free from combination 1 grain of hydrogen, 
104 of lead, 108 of silver, 39 of potassium, and 31.6 of copper. 
These are the combining numbers of those elements, and establish 
a remarkable equivalency between chemical and electrical forces. 

410. Atomic Heat. — The definite relation between combining 
numbers and specific heats is equally remarkable. For example, 
28, 32, 103 are the atomic numbers of iron, copper, and lead ; 
but they also express the relations of these bodies to heat. They 
indicate the exact quantities of the metals which will be raised 
through equal temperature by equal sources of heat. It would 
take the same amount of burning alcohol to heat 28 lbs. of iron 
100° that would be consumed in raising 32 lbs. of copper or 103 > 
of lead through the same number of degrees. The correspondence 
is very close with the other metallic elements and with sulphur, 
while the atomic heat of several of the elements is double that of 
the bodies mentioned. 

411. Units of Heat and Force.— To ascertain at what rate 
mechanical force produces heat, requires certain standards of com- 
parison, known as the units of heat and force. The English unit 
of heat is 1 lb. of water raised through 1 degree of Fahrenheit ; 
the unit of force is 1 avoirdupois pound falling through 1 foot of 
space ; or, as it is called, the foot-pound. 100 lbs. of water raised 
through 10°, would require 1,000 units of heat ; while 100 lbs. 
falling through 10 feet would produce 1,000 units of force. 

412. The Mechanical Equivalent of Heat. — To Dr. Joule, of 
Manchester, England, is due the honor of having experimentally 

relation between fuel, heat, and work ? What did Far ad ay find to be the rela- 
tion between chemical action and electricity ? Examples. 410. What is said of 
the relation between combining numbers and specific heats ? Examples. 411. 
What are the units of heat and force? 412. Who determined the mechanical 



CONSERVATION OF FORCE. 173 

demonstrated the mechanical equivalent of heat; — that is, how 
many units of force are equal to a unit of heat. He agitated 
water, mercury, and oil successively, in suitable vessels, by means 
of paddles driven by falling weights, and determined the exact 
amount of force spent, and of heat produced. He also rubbed 
cast iron discs against each other, carefully measuring the force 
employed and the resulting heat. By varied and repeated experi- 
ments he found that the same expenditure of power produced the 
same absolute amount of heat, whatever materials were used; 
and that a pound weight falling through 772 feet, or 772 lbs. fall- 
ing through 1 foot, and then arrested, produce sufficient heat to 
raise 1 lb. of water 1° ; so that the unit of heat is equal to 772 
units of force. This is known as - Joule's Law.' * 

41 3. Further Links of the Dynamic Chain. — The law of equi- 
valence between mechanical energy and heat thus directly estab- 
lished is beautifully confirmed by introducing other links of force. 
An electric current, which, by resistance in passing through an im- 
perfect conductor, produces sufficient heat to raise 1 lb. of water 
1 degree, sets free an amount of hydrogen which, when burned, 
raises exactly 1 lb. of water 1 degree. And again, the same 
amount of electricity will produce an attractive magnetic force by 
which a weight of 772 lbs. may be raised 1 foot high. 

414. Significance of Joule's Law.— The establishment of the 



* It is worth while here to note that the first step in these grand views of the 
forces which have been recently unfolded, was taken toward the close of the last 
century by an American, Benjamin Thompson, afterward known as Count 
Rumford. He went to Europe in the time of the revolution, and, devoting himself 
to scientific investigations, became the founder of the Royal Institution of Eng- 
land. He exploded the notion of caloric, demonstrated experimentally the con- 
version of mchanical force into heat, and arrived at quantitative results which, 
considering the roughness of his experiments, are remarkably near the establish- 
ed facts. He revolved a brass cannon against a steel borer by horse power for 2\ 
hours, and generated heat enough to raise 18| lbs. of water from 60° to 212°. He 
explicitly announced the view now held of the nature of heat, and wrote as fol- 
lows, the italics being his own : ' What is heat? Is there any such thing as an 
igneous fluid 1 Is there any thing that with propriety can be called caloric ? We 
have seen that a very considerable quantity of heat may be excited by the friction 
of two metallic surfaces, and given otf in a constant stream or flux in all direc- 
tions without interruption or intermission, and without any signs of diminution 
or exhaustion. In reasoning on this subject we must not forget that most remark- 
able circumstance, that the source of the heat generated by friction in these ex- 
periments appeared to be inexhaustible. It is hardly necessary to add that any 
thing which any insulated body or system of bodies can continue to furnish icithoiit 
limitation, cannot possibly be & material substance; and it appears to me to be 
extremely difficult, if not quite impossible, to form any distinct idea of any thing 
capable of being excited and communicated in these experiments, except it be 
motion.' 

equivalent of heat? What is it? How was it ascertained? Wliat is Joule's 
law? 413. How is the law of equivalence between mechanical energy and heat 



174 CHEMICAL PHYSICS. 

principle of correlation between mechanical force and heat con- 
stitutes one of the most important events in the progress of sci- 
ence. It teaches us that the movements we see around us are not 
spontaneous, or independent occurrences, but links in the eternal 
chain of forces : that when bodies are put in motion, it is at the 
expense of some previously existing energy, and that when they 
come to rest, their force is not destroyed, but lives on in other 
forms. Every motion we see has its thermal value ; and when it 
ceases, its equivalent of heat is an invariable result. Should the 
motion of the heavenly bodies be arrested, it would produce a 
conflagration of the universe. 

415. As the motions and masses of the planetary bodies are 
definite and determined, we can predict the exact consequence if 
those motions should cease. The earth is 8,000 miles in diameter, 
5-J times heavier than water, and moves through its orbit at the rate 
of 68,000 miles an hour. Were its motion suddenly arrested it 
would generate a heat equal to the combustion of 14 globes of an- 
thracite coal as large as the earth. Should it fall into the sun the 
shock would produce a heat equal to the combustion of 5,400 earth- 
globes of solid coal. If the sun were a solid mass of anthracite his 
combustion would maintain the present heat but 5,000 years; 
whereas, if the planet, Jupiter, should fall into the sun it would 
produce heat enough -to maintain the solar emission for 35,000 
years (1196). 

416. If a fragment of coal were taken to the sun and burned it 
would give out a definite amount of heat, but if it should fall from 
the earth to the sun it would produce 3,000 times more heat by 
its arrested motion. It has been suggested that meteoric matter 
falling into the sun may be the actual cause of his heat. 

417. Motion alone convertible. — As two substances when 
combined chemically, produce heat, and remain combined, it may 
be asked, ' How can the heat be regarded as converted chemical 
force, while that force is still in action ? ' This will be understood 
by referring to the case of gravity. When a lifted body falls, it 
gives back the force expended in lifting it, but gravity still attracts 
it to the earth with undiminished force. So with the chemical 

confirmed? 414. What does this principle teach us? Wb at would result if the 
movement of the heavenly bodies should be arrested? 415. What if the earth's 
motion were suddenly stopped ? Mention some further facts in this connection. 
416. What is said of a fragment of coal ? 417. How can the heat be converted into 



CONSERVATION OF FORCE. 175 

atoms. They are detached, and then rush together again, giving 
back a force equal to that employed in separating them ; but they 
remain combined as the weight remains pressed to the ground. 
Neither gravity nor affinity are for an instant suspended; they 
are in constant action and are only resisted by antagonist forces: 
the amount of motion which results from this resistance measures 
the convertible force. Only force in action — which is known as 
living force, or vis viva — is convertible. 

418. Relations of Matter and Force. — In the study of nature, 
questions of force are becoming more and more prominent. The 
things to be explained are changes — active effects — motions in 
ordinary matter, and the tendency is to regard matter, not as 
acted upon, but as in itself inherently active. The chief use of atoms 
is to serve as points or vehicles of motion. Thus the study of 
matter resolves itself into the study of forces. Inert objects, as 
they appear to the eye of sense, are replaced by activities revealed 
to the eye of intellect. The conceptions of 'gross,' 'corrupt,' 
* brute matter,' are passing away with the prejudices of the past, 
and in place of a dead material world, we have a living organism 
of spiritual energies. 

419. The principle of the correlation of forces is one of the 
most fruitful and far-reaching that science has established. Its 
introduction forms one of those intellectual epochs which change 
the standpoint of the philosopher, revealing old questions in new 
aspects, and bringing many new ones into view. It teaches with 
a new emphasis the great lesson of the unity of the universe, and 
the brotherhood of the agencies through which it is governed. 
And as the policy of the Divine Administration is one, there can 
be no doubt that the principle applies not only to physical forces, 
but to all forces. Its operation has been traced, as we shall see, 
in the field of organization, and it opens a new and promising 
method of studying the various activities of human society. 

chemical force while that force is still in action ? 418. What are to be regarded in 
studying nature? State the chief use of atoms. What is said of force and mat- 
ter ? 419. Of the principle of the correlation of the forces ? 



PAET II. 
INORGANIC CHEMISTRY. 



ORIGIN OF THE SCIENCE — ALCHEMY. 

420. The Four Ancient Elements.— Thoughtful minds, as we 
have previously stated, never rest satisfied with appearances; 
they always seek for reasons and causes. This was the case in the 
most ancient times in regard to the objects of nattff e. They were 
held to be, not what they seemed, but formed of various commix- 
tures of four elements, fire, air, earth, and water, and for thou- 
sands of years the properties and changes of all substances, 
animate and inanimate, were explained on this hypothesis. 

421. This view was not without its philosophy. All bodies, 
it was said, must be either hot or cold, moist or dry. These are 
fundamental properties, and their various unions produce the four 
elements thus : 

Dryness and Warmth and Moisture and Dryness and 

Warmth produce Moisture — Cold — Cold — 

Fire; Air; Water; Earth. 

These elements fire, air, earth, and water, may be transmuted into 
each other by exchange of properties. Thus, if cold is added to 
air it destroys the warmth and converts it into water : by the 
substitution of dryness for moisture, water is transformed into 
earth ; while, by reversing these changes, earth becomes water, 
and water, air. Thus, by the communication of properties, all 
things were supposed to be produced, the predominating element 
giving character to the body. 

prejudices are passing away? 420. How were the objects of nature regarded in 
ancient times? 421. How were these elements produced? How transmuted? 



ORIGIN OF THE SCIENCE — ALCHEMY. 177 

422. The Foundation of Alchemy. — The leading idea of the 
doctrine of the four elements was the instability of the properties 
of matter. They were held to he like clothes which are put on 
and off at will — mere shifting and communicable things, the addi- 
tion or subtraction of which transformed one substance into 
another. Water was poured upon quick lime ; it disappeared and 
was transmuted ; that is, it lost the properties of water, and ac- 
quired those of stone. A small plant in a weighed portion of 
soil, by the addition of pure water only, grew into a vigorous 
shrub, increasing many pounds in weight, while the soil lost but a 
trifle. What more natural, therefore, than to suppose that water 
was ' transmuted ' into a living structure. This ancient and deeply 
established belief was the starting point of the labors of the al- 
chemists, who were the earliest chemists. 

423. For centuries, philosophy had taught that the properties 
of matter are transferable ; ' then,' said the alchemists, 'let us trans- 
fer to lead and iron the properties of gold ! ' All bodies having 
a metallic lustre and appearance, they naturally regarded as 
metals ; such as preserved this lustre when exposed to fire, were 
called noble, or perfect metals, while those which lost their lustre 
and malleability by heat were termed base metals. The metals 
were, moreover, regarded as compounds consisting of opposite 
elements, one of which made them pure, and the other base, their 
rank being determined by the relative proportions of these elements. 

424. Plausibility of the Idea. — Nor were these views mere 
idle speculations ; they seemed strongly supported by facts. The 
alchemists saw that the lead ore — galena, had the metallic lustre and 
color of lead ; they, therefore, believed it to be a real metal. But, 
if heated, it gave off sulphur, while, at the same time, ail its 
metallic properties — lustre, malleability, and fusibility — were 
heightened, and it became true lead, or a more perfect metal. 
What more reasonable than to suppose, that by the separation of 
a little more sulphur, it might be still further purified, and 
changed to silver ? And when, on further application of heat, a 
certain amount of silver was actually obtained from the lead, and 
from this silver a trace also of gold, it was not surprising that the 

422. What was the leading idea of this philosophy? What common phenomena 
were interpreted as instances of transmutation ? What did the alchemists pro- 
pose? What bodies were called metals? How were they divided? What was 
their composition? 424. By what experiments and reasoning did they sustain the 



178 INORGANIC CHEMISTRY. 

alchemist should honestly believe that he had created the three 
metals, and that by perfecting the operation, he could convert all 
his galena into gold. 

425. Again, the alchemists knew that the brilliant metal mer- 
cury volatilizes by heat and disappears in invisible vapor. Hence 
when a base metal lost its lustre in the fire, or rusted in the air, 
they supposed it was caused by the escape of the volatile mercury, 
which they regarded as the pure metallic principle. Thus, by 
diminishing their sulphur and increasing their mercury, the 
alchemists expected to finally perfect or ennoble all the base 
metals ; — that is, turn them into gold. The wondrous substance 
which should have the power of expelling the sulphur, fixing the 
mercury, and thus accomplishing transmutation, was universally 
believed in and sought for under the name of the Philosopher's 
Stone. 

426. The alchemists, moreover, drew support for their belief 
from all imaginable sources. The metals were held to grow like 
plants, and the philosopher's stone was, therefore, the seed of 
gold. They said also, ' Does not fermentation transmute the sweet 
juices of plants into the invigorating and youth-giving water of 
life (aqua vitse, alcohol) ? Does not digestion transform food into 
blood V In a decree of 1423, Henry VI., of England, declared 
' that the clergy should engage in the search for the philosopher's 
stone, for since they could change bread and wine into the body 
and blood of Christ, they must also by the help of God succeed in 
transmuting the baser metals into gold.' 

427. But the doctrine was carried much farther. If the metals 
might be thus transformed, what should limit the magical power 
of the transforming agent ! Other transmutations were equally 
possible, as that of weakness, pain, and disease into robust and 
perennial health, and thus the marvellous stone became also a 
universal medicine : or it might even change the decrepitude of old 
age back to the vigor and fire of youth, and thus become the elixir 
of life. 

428. Motives of the Alchemists. — We can now comprehend 
the power of the ruling motive that first drove men to investiga- 
tion. The love of knowledge and the desire to explore the secrets 

idea? 425. What was the philosopher's stone? 426. What other common changes 
gave support to the belief? 427. What led to the search for a universal medicine and 
the elixir of life ? 428. Why was alchemy necessary ? 429. What instances arc given 



ORIGIN OF THE SCIENCE — ALCHEMY. 179 

of nature in quest of truth, were not sufficiently strong incentives 
in those days of darkness and ignorance. A mighty incitement 
was required that should rouse the most powerful passions of 
human nature, and this was providentially furnished by the belief 
in the philosopher's stone. Its possession would secure all the con- 
ditions offcearthly happiness — boundless wealth, perpetual health, 
eternal youth ! — and for these ineffable prizes the alchemists labor- 
ed day and night, devising experiments, inventing processes, ran- 
sacking nature in a thousand directions, and putting her to every 
conceivable torture to wring out the wondrous secret. The ob- 
ject sought was not attained, but the foundations of chemistry 
were laid. Men working in the direction of an illusive purpose 
made many discoveries which they could not appreciate, but which 
were invaluable to the world. 

429. Results of their Labors. — For example, a cobbler of Bo- 
logna, named Cascaeiolo, who divided his time between shoe- 
mending and alchemy, discovered in one of his rambles a heavy 
stone now known as the sulphate of baryta. In experimenting 
with it he obtained, instead of gold, a most extraordinary sub- 
stance — 'a light magnet,' i which absorbed the rays of the sun 
by day to emit them by night.' The cobbler was in ecstasy ; if the 
strange body could absorb the golden light of the sun, it might 
surely convert the base metals into gold — the sol of the alchemists. 
Thus was discovered the sulphur et of barium, the first substance 
known to become phosphorescent by solar action. Again, an 
alchemist in Hamburg, named Beandt, long baffled in the search 
for the philosopher's stone, reflecting one day on the yellow color 
of urine, suspected that it might contain some gold-engendering 
principle. He began experimenting, and, after years of toil, at 
length discovered, not gold, but phosphorus ! In the same way, 
the alchemists sought for the alcahest — the liquid that should 
dissolve all thiugs; they failed, but discovered those powerful 
solvents — sulphuric, nitric, and muriatic acids, which have largely 
contributed to the arts of civilization. So the search for the elixir 
of life revealed many precious substances for the alleviation of 
suffering and the increase of human enjoyment. 

430. Vitality of their Idea.— The power and persistence of the 
fundamental idea of the alchemists are surprising. It was only 

where the search ended in discovery ? 480. What is said of the persistence of this 
belief? 431. How must alchemy he interpreted? What is its relation to chem- 



180 INORGANIC CHEMISTRY. 

near the close of the last century that the ancient belief in the 
transmutation of the elements was finally overthrown ; and we 
can now hardly conceive how deeply it was interwoven with 
universal thought. The great French chemist Lavoisier gave a 
course of public lectures with elaborate experiments to show that 
water could not be transmuted into earth ; while an Italran philos- 
opher went carefully into the proof that water from melted Al- 
pine snows was of the same nature as that from common springs 
and wells. 

431. Alchemy, it is well known, was mixed up with magic, 
astrology, and various gross impostures, yet those who denounce 
it as utterly visionary and absurd, profoundly misread this chapter 
of man's mental history. Alchemy formed a natural stage in the 
growth of the human mind, and must be interpreted in connection 
with its period. It was the offspring of the old philosophy, but 
the parent of modern chemistry, and must always have a memor- 
able interest as the first experimental grapple of man with nature. 



CHAPTEE YII. 

THE ATMOSPHERIC ELEMENTS. 
(ORGANOGENS.) 

432. Inorganic Chemistry is that branch of the science which 
treats of the properties of the chemical elements, and of the com- 
pounds they form, independent of the influence of life. 

433. Classification of the Elements. — The simple bodies are 
divided into two classes, metals and metalloids, or non-metallic 
elements. This general distinction is obvious and useful, but it 
corresponds to no clear line in nature, as the elements pass into 
each other gradually, two or three being ranked by some as 
metals, and by others as metalloids. 

434. We first consider these four remarkable elements, Oxy- 
gen, Hydrogen, Nitrogen, and Carbon, which have the leading 

istry? 432. What is inorganic chemistry? 433. How are the simple bodies 
divided? Why is this distinction faulty? 434. What elements do we first con- 



OXYGEN". 181 

share in the world's economy. They form the atmosphere, and 
atlf therefore, termed the Atmospheric Group. They are, also, 
the chief constituents of the vegetable and animal world, and are 
hence called Organogens — generators of organization. Next come 
Chlorine, Iodine, Bromine, and Fluorine, bodies which combine 
with metals forming saline compounds, of which common salt is a 
type, and hence called by Beezelius, Halogens, or salt formers. 
Sulphur, Phosphorus, Selenium, and Tellurium form a combus- 
tible group termed Pyrogens, or fire producers. Lastly, Silicon 
and Boron are associated together as Hyalogens, or glass formers. 

§1. Oxygen. 
Symbol, 0. Equivalent, 8. Specific Gravity, 1.1087. 

435. We begin the study of chemical substances with that 
most remarkable and important element, oxygen gas. The word 
gas, which is applied to thin vaporous bodies like air, was first 
used in the seventeenth century, and is an interesting memorial 
of the state of mind out of which the science of chemistry grew. 
It had been observed that strange things occurred in certain 
mysterious places, as churchyards, caves, and the bottoms of 
mines and wells ; — there were lurid flames and sulphurous fumes, 
violent explosions, and sudden death. These were supposed to be 
the work of invisible spirits. In the operations of alchemy, ves- 
sels would often explode with danger to those around, and this 
also was attributed to the vexed and imprisoned spirits who thus 
avenged themselves upon their tormentors. ' The devout alche- 
mists, therefore, commenced their experiments with prayer, and 
stamped upon their vessels the mark of the holy cross ; — hence 
the name crucible? To these invisible agents, Yon Helmont 
first applied the term gas, from gahst- or geist, a ghost or spirit. 
The terms spirit of wine, spirit of nitre, &c, are also significant 
of the superstitions of those early times. 

436. Discovery of Oxygen. — This gas was discovered by Dr. 
Priestley, of England, in 1774, and rediscovered in the following 
year by the Swedish chemist, Scheele.^ Its discovery is also 
claimed by the French chemist, Lavoisier. There was a beautiful 

eider? What are they called, and why? How are the remaining metalloids 
grouped? 435. What is a gas ? Whence is the term derived ? Origin of the term 
crucible 7 436. When and by whom was oxygen discovered ? What is said of the 



182 INORGANIC CHEMISTRY. 

significance in the form of Pkiestley's celebrated experiment. He 
submitted one of the compounds of mercury to the rays of the sun, 
concentrated by a burning-glass, when oxygen was set free. It was 
fitting that the sun, who, by his chemical relation to oxygen, con- 
trols the destiny of the living world, should himself first summon 
this wonderful agent into the conscious presence of man. 

437. Its Importance. — This has been justly pronounced the cap- 
ital discovery of the last century, rivalling in importance the great 
discovery of gravitation, by Newton, in the preceding century. It 
formed one of the great eras in the progress of human knowledge ; 
it put an end to old theories, laid the foundation of modern chemical 
science, and furnished the master key by which man has been enabled 
to open the mysteries of nature. But while the discovery of gravi- 
tation is unsurpassed in grandeur, that of oxygen is far more vitally 
linked with the course of earthly affairs. 

438. Of its vast practical consequences, Prof. Liebio observes: 
1 Since the discovery of oxygen, the civilized world has under- 
gone a revolution in manners and customs. The knowledge of 
the composition of the atmosphere, of the solid crust of the earth, 
of water, and of their influence upon the life of plants and 
animals, was linked with that discovery. The successful pursuit 
of innumerable trades and manufactures, the profitable separation 
of metals from their ores, also stand in the closest connection 
therewith. It may well be said that the material prosperity of 
empires has increased manifold since the time oxygen became 
known, and the fortune of every individual has been augmented 
in proportion.' 

439. Preparation. — Oxygen may be procured in many ways. 
To obtain a large supply, we may heat to redness black oxide 
of manganese in an iron bottle, fitted with a delivering tube 
through which the liberated gas escapes. A pound of this oxide 
usually yields about 1,400 cubic inches of impure gas. The chem- 
ical changes which take place may be thus expressed in symbols : — 

3Mn 2 , give Mn O, Mn a 3 +20 : 
that is, the peroxide of manganese is changed to two other com- 
pounds, and loses one third of its oxygen in the process. 

440. By a New Process. — It has lately been found that by 

discovery ? How did Priestley make the discovery ? 438. What does Prof. 

Liebig say of it ? 439. What is the common method of obtaining oxygen ? What 



OXYGEN. 



183 



mixing nitrate of soda, NaO, N0 5 , with crude oxide of zinc, ZnO, 
in the proportion of 10 lbs. of the former to 20 lbs. of the latter, 
and heating them to redness in an iron retort, a large amount of 
oxygen is rapidly given off, diluted with about 40 per cent, of 
nitrogen. The mixed product contains about three times as much 
oxygen as the air, and may prove valuable for some heating and 
illuminating purposes, as its cost is said to be but one fifth that 
of oxygen by any other process. 

441. From Chlorate of Potash. — It can be obtained still more 
pure, and very readily from Fiq 16gj 

chlorate of potash. Two or 

three hundred grains of the salt 

are placed in a glass retort, 

which is fitted tightly with a 

cork containing a glass tube, 

bent so as to dip under the shelf 

of the pneumatic trough, Fig. 

168. The retort is heated, and 

the chlorate gives off more than 

a third of its weight of gas, an 

ounce furnishing nearly two 

gallons. This salt consists of chloric acid and potash, and in the 

change chloride of potassium is formed, the whole of the oxygen 

being disengaged — thus 

KO,ClQ 5 =KCl+60. 
The decomposition of the chlorate is much facilitated by mixing 
with it one fourth its weight of oxide of copper, or black oxide of 
manganese thoroughly dried. These substances take no active 
part in the change, but seem to aid the decomposition by simple 
presence (catalysis). 

442. The Pneumatic Trough is a vessel by means of which 
gases are collected. It is usually filled with water, just under the 
surface of which there is a perforated shelf for the support of 
jars, Fig. 168. The jar, filled with water, and inverted, is lifted 
nearly out of the liquid, and slid upon the shelf; the water being 
supported above its level by atmospheric pressure (563). A con- 




Making Oxygen. 



is the chemical change? 440. Describe the new process? For what may it per- 
haps be used ? 441. How is it obtained from chlorate of potash ? Explain the 
re-action. How may the change be facilitated? 442. Describe the pneumatic 



184 



INOEGANIC CHEMISTET. 



Fig. 169. 




Pneumatic Trough. 



veying tube bends under the shelf, from which the delivered gas 
rises into the jar, displacing the water. It may be then slid off, 
month downward, into a shallow vessel, containing a little water, 
and kept for use. In Fig. 168, the trough is represented as having 
glass sides which are very convenient for showing effects in the 

lecture room. The best form is 
that of a cistern, Fig. 169, so deep 
that jars may be conveniently in- 
verted in it, and with a large shelf 
for holding several of them. Gases 
may be transferred from one ves- 
sel to another by pouring them 
upward, as shown in Fig. 169. 
The vessel to be filled with gas is 
first filled with wafer, inverted, 
and its mouth raised nearly to the 
surface of the liquid. The mouth 
of the vessel containing the gas is then brought under the other 
by gentle inclination, and the gas rises in bubbles, displacing the 
water, and filling the second jar. 

443. Physical Properties of Oxygen. — Oxygen is a transpa- 
rent, colorless, tasteless, inodorous gas, about T ^ heavier than the 
atmosphere, and forming 23 per cent, of its weight. It refracts 
light the least of any known substance, and has never been con- 
densed into a liquid. It possesses weak magnetic properties, but 
loses them at a high temperature. The magnetic effect of atmo- 
spheric oxygen has been estimated as equal to a film of iron cov- 
ering the earth -^ of an inch in thickness, and, as this property 
varies with the daily temperature, it is supposed that it may be 
concerned in the diurnal fluctuations of the needle. Oxygen is 
slightly soluble in water, 100 gallons of which absorb about 4£ 
of the gas. 

444. Its Chemical Properties. — Oxygen is perfectly neutral, 
possessing neither acid nor alkaline qualities ; but, though mild and 
bland and apparently the very type of passiveness, this substance is 
endowed with the most extraordinary power. Its attractions are 
the most intense and varied of all the elements. So remarkable is 



trough. How is it used ? What is the best form ? How is pouring upward 
effected ? 443. What are the physical properties of oxygen ? Its magnetic effect 
in the atmosphere ? To what degree is it soluble ? 444. What are its chemical 



OXYGEN. 



185 



Fig. 170. 



its adaptive power that it combines with every one of the simple 
bodies (except, perhaps, fluorine), giviDg rise to compounds of the 
most opposite and diverse properties. A glance at the chemical 
chart shows the wide range of its affinities. "With some elements 
it forms gases, with others liquids, and with others solids. Some 
it holds so slightly that they are readily separated, and others it 
seizes with such power that the utmost skill of the chemist is 
tasked to force them asunder. Uniting with one set of bodies, it 
gives rise to neutral compounds, with another to corrosive acids, 
with another to burning alkalies. With some elements it forms 
nourishing food, with others deadly poisons ; mingled with an in- 
visible body like itself, it forms the air we breathe, and united 
with another twenty times lighter and rarer than itself, it pro- 
duces the water we drink. 

445. The oxygen of the air (about 
one fifth of its weight), is equally diffused 
throughout it, and exists in a free or uncom- 
bined condition. All combustion in the 
open air is the result of the action of oxy- 
gen. It has a powerful affinity for the ele- 
ments of which fuel is composed, and unites 
with them with such violence as to give 
rise to the heat and light of our ordinary 
fires, as we shall see in Combustion (588.) 

446. Combustion in Oxygen. — All sub- 
stances which burn in air, burn in pure oxy- 
gen with greatly increased brilliancy. If the 
flame of a taper, Fig. 170, be extinguished, 
and a single spark remain upon the wick, on 
plunging it into a jar of pure oxygen, it will 
be re-lit and burn with extreme vividness ; 
and this may be repeated many times in the 
same vessel of gas, The combustion of a 
splinter of wood is brilliant, and a piece of 
bark charcoal glows and scintillates in the 
most beautiful manner. 

447. Substances usually considered in- 

properties ? What extraordinary power does it possess ? A glance at the chart 
shows what ? Give examples. 445. In what state does oxygen exist in the air ? 
What is its office in combustion? 446. Describe the experiment, Fig. 170? 




Taper in Oxygen. 



Fig. 171. 




Combustion of Iron in 
Oxygen. 



186 



INORGANIC CHEMISTEY. 



Fig. 172. 




combustible also burn violently in oxygen. If a piece of fine iron 
wire (or, better still, a steel watch spring) be coiled into a spiral 
and then tipped with sulphur, ignited and introduced into a jar of 
oxygen, it burns with dazzling brilliancy and splendid corr loca- 
tions, Fig. 171. Occasionally globules of white-hot iron fuse into 
the glass even through an inch depth of water. 

448. If a jar of oxygen be inverted over a stand upon which 
there is a little burning sulphur, a beautiful blue light is emitted, 
and the fumes produced circulate round in cu- 
rious rings, Fig. 172. If phosphorus be burned 
in the same manner, a blinding flood of light is 
produced, accompanied with great heat. In all 
these cases, the effects are simply due to the 
union of oxygen with the burning body, and 
could we have weighed them before the experi- 
ment, and the products of combustion after- 
ward, they would have been found precisely v 
equal. 

449. Slow Oxidation.— The combustion of 
oxygen with the elements is called oxidation, 
and the products oxides. The cases of combus- 
tion we have been considering are examples of 
rapid oxidation, but oxygen frequently enters 
into slow combination at ordinary temperatures 
and without perceptible heat, as in the rusting 
of iron in the air. Heat, however, always ac- 
companies this slow combustion. An ounce of 
iron rusted in air, or burnt in oxygen, produces 
the same amount of heat, but in the former case it requires years 
for its development, and in the latter only as many minutes. 
Sometimes, under favorable circumstances, the oxidation becomes 
so rapid that the accumulated heat produces ignition, causing the 
phenomenon called spontaneous comotistion. This is most liable 
to occur with porous substances which expose a large surface to 
the air. The tow or cotton used for wiping the lubricating oil 



Burning of Sulphur. 



Fig. 173. 




Phosphorus burn- 
ing in Oxygen. 



447. What does Fig. 171 represent ? 448. What effects are seen when sulphur and 
phosphorus are burned in oxygen ? To what are they all due ? 449. What is 
oxidation? What are oxides? How does slow differ from rapid combustion? 
What is spontaneous combustion ? Where is it most likely to occur ? 450. What 



OXYGEN. 187 

from machinery, and then laid away in heaps, often ignites in this 
manner, especially if exposed to the sun. 

450. Eremacausis. — The cause of decay in vegetable and ani- 
mal substances is the action of oxygen which breaks them up into 
simpler and more permanent compounds. This slow combustion 
is called by Liebig- eremacausis. Oxidation is also the grand pro- 
cess by which the earth, air, and sea are purified from contamina- 
tions ; noxious vapors and pestilential effluvia being destroyed by a 
process of burning, more slow indeed, but as real as if it took place 
in a furnace. The offensive impurities which constantly flow into 
rivers, lakes, and oceans, as well as the decaying remains of the 
living tribes which inhabit them, are perpetually oxidized by the 
dissolved gas, and the water thus kept pure and sweet. For this 
reason waters that have become foul and putrid are purified and 
sweetened by exposure to the action of air. This effect, however, 
is largely dependent upon a condition of oxygen which has been 
but lately discovered (456). 

451. Relation of Oxygen to Life. — Oxygen is the universal 
supporter of respiration, and, as this is the most important of the 
vital processes, it is hence the immediate supporter of life. From 
this circumstance it was first known as vital air. An animal con- 
fined in a given bulk of common air, having consumed its oxygen, 
dies. If immersed in pure oxygen, it lives much longer, but the 
effect is too powerful — over-action, fever, and in a short time 
death, are the result. As the introduction of oxygen is the prime 
physiological event of animal life, the mechanism of all living 
beings is constructed with reference to this fact. The lungs of the 
higher races, the spiracula of insects, and the gills of fishes, are 
all adapted to the same purpose — the absorption of oxygen, either 
from the air or water. The animal organism is chiefly composed 
of combustible constituents, and we introduce this wonderful 
element incessantly, day and night, from birth to death, that it 
may perform its chemical work.- The animal body is an oxidizing 
apparatus, in which the same changes occur that take place in the 
flame, only in a lower degree, and a more regulated way. Every 

is the cause of decay ? What is it called ? What is said of oxygen as a purifier ? 
451. Why was oxygen called vital air? When an animal is confined in a limited 
portion of air, what follows ? What if in pure oxygen ? How are all animals con- 
structed ? Of what are they composed ? What are they all incessantly doing ? 
For what purpose ? What is going on in the animal system ? Why is food taken ? 



188 INOEGANIC CHEMISTRY. 

organ, muscle, nerve, and membrane is wasted away, burnt to 
poisonous gases and ashes, and thrown from the system as dead 
and dangerous matter. If these constant losses are not repaired 
by the due supply of food, emaciation, decay, and finally death 
ensue. Starvation is thus unimpeded oxidation — slow burning to 
death. 

452. Rate of Consumption of Oxygen.— Of the 15 lbs. of air 
over every square inch of the earth's surface, one fifth is oxygen. 
A man consumes by respiration about 2 lbs. each day ; that is, he 
withdraws daily all the oxygen from a column of air two thirds 
of an inch square, and reaching to the top of the atmosphere, or 
45 miles high. In a year he removes all the oxygen over a space 
of 243 square inches, and in 70 years from an area 118 feet square. 
Six pounds of pure coal, in burning, consume 16 lbs. of oxygen; 
a steamship, therefore, which should burn 1,100 tons of coal in 
crossing the Atlantic, would consume nearly 3,000 tons of oxygen. 
Assuming the population of the globe 1,000,000,000, and that each 
individual in respiration requires but 1 lb. per day, assuming as 
much more for the processes of combustion ; and twice as much 
for the respiration of the animal kingdom, and then doubling this 
whole quantity for the universal and unceasing functions of decay 
(probably far too low an estimate), we have an aggregate of over 
7,000,000 tons of oxygen withdrawn from the atmosphere each 
day. The oxygen in the atmosphere is computed to be about 
1,178,158,000,000,000 tons, which, if separated from the air, and 
forming a layer of uniform density upon the earth, would be one 
mile deep. 

453. Oxygen in the World of Waters.— Enormous as this 
quantity seems, it is in rearlity but the bare starting point — the 
unit of that stupendous scale of prodigality, with which this 
element has been distributed in nature. Oxygen, condensed into 
800 times less space, is the chief constituent of water, forming £ 
of its weight. The ocean covers two thirds of the earth, and is 
estimated as averaging two miles in depth.- Could the oxygen 
imprisoned in this liquid form be set free, it would be sufficient to 

What is starvation? 452. How much oxygen does a man' consume in a day? 
From how much air is the oxygen removed in the same time ? In a year ? In 70 
years ? What is the estimate concerning a steamship ? What is the whole amount 
of oxygen in the atmosphere, and how much is consumed each day ? 453. What 
proportion of water is oxygen? If this were set free, what would it form? 



OXYGEN. 189 

form an atmosphere around the globe, nearly a thousand miles 
deep, and of the same density as that now at the level of the sea! 

454. Proportion in the Solid Earth. — And these proportions 
are as nothing compared to the incalculable quantities of oxygen 
wrought into the solid fabric of the world. Of the three min- 
erals which form the chief mass of the earth's crust, silica, 
alumina, and lime, the first, and by far the most extensively dis- 
tributed, contains more than one half its weight of oxygen, and 
the other two almost one half. It constitutes, also, three fourths 
of the weight of all animal bodies, and four fifths of that of the 
vegetable world. Thus, one half the ponderable matter of the 
earth, so far as man has explored it, is made up of a single chemical 
element, while the crowning wonder is, that when called up before 
us by the magic of chemistry, it is but an invisible gas, — no man 
has ever beheld it, — it seems the very type of spiritual existence 
and invisible power ! 

455. Office in Nature. — The part played by oxygen in the 
scheme of nature is imposing in the highest degree. In virtue of 
its boundless abundance, its diffusive nature, the vast range and 
strength of its attractions, and the unchangeableness of its com- 
binations, it would seem to have been appointed to the grand 
office of taking charge of all the other elements, and bringing 
them into an orderly and permanent system. The rocks and 
waters of the earth consist of materials given over to its custody. 
Saturated with it they are in a condition of the most perfect 
chemical stability. Enveloping our planet in its free condition, it 
manifests an irresistible passion to seize upon and possess all 
things. The deadly foe of life, it would destroy all organized 
beings, and pursuing them to the very tomb, decompose and dis- 
solve their structures, carrying back their elements to the quiescent 
mineral world. This element has, therefore, been personified as 
the genius of the air — an omnipresent, destructive spirit, which 
holds the globe in its consuming embrace ; which revels in con- 
flagration, and would reduce all things to ashes and rest. But the 
earth has not been left to the operation of its own forces. Celes- 
tial radiations are the antagonists of oxygen, and their agency in 
saving the world from its desolating influence, will be shown 
when we consider the subject of Physiological Chemistry (1194). 

454. What proportion of the earth's crust is oxygen? Of animal bodies? Of 
vegetables ? What is said to he the crowning wonder of aU this ? 455. What is 



190 



IKOEGANIC CHEMISTRY. 



Fig. 174. 




Making Ozone. 



§11. Ozone — Allotropic Oxygen. 

456. How Produced. — When electric sparks are passed through 
dry air, a peculiar odor is perceived which has been called the 
4 electrical smell.' There was much doubt about the cause of it, 
until the investigations of Prof. Schonbein showed that it was 

an allotropic form of oxygen. From its 
peculiar odor, its discoverer named it 
ozone. Oxygen may be converted into 
ozone, not only by electricity, but in va- 
rious other ways. If a piece of phospho- 
rus be placed in a jar, and partially covered 
with water, its slow oxidation will soon 
produce ozone. Or, if we place a little 
ether in an open vessel, and then introduce 
into its vapor a moderately heated glass 
rod, Fig. 174, ozone promptly appears. If 
it be passed through a red-hot tube, it will be changed into com- 
mon oxygen, and even a temperature scarcely above that of boil- 
ing water robs it of all active power. 

457. Properties and Test of Ozone.— Ozone seems to be oxygen 
greatly intensified in activity. It is armed with a new energy, and 
is capable of producing changes which, in its ordinary state, are 
impossible. It corrodes metals upon which before it could not act, 
for example, silver ; it quickly bleaches out colors, which are com- 
paratively permanent in the air ; it deodorizes tainted flesh, de- 
stroying its effluvium instantly, and carries woody fibre in a short 
time through a course of decomposition, which, with common 
oxygen, would require years. This increased activity becomes the 
test of the allotropic condition. Ozone replaces iodine in its com- 
bination with the metals ; an effect oxygen cannot produce ; 
hence it decomposes iodide of potassium, setting free the iodine. 
Free iodine combines with starch, turning it blue ; therefore, a 
test of ozone is made by soaking slips of paper in a mixture of 
starch and iodide of potassium. The slightest trace of ozone 



said of the office of oxygen in nature ? 456. "What is ozone ? How is it produced ? 
By what is it destroyed ? 457. What are the properties of ozone ? What is the 
test of its presence? Give examples? What is its effect when breathed? 



OZONE — AIXOTEOPIC OXYGEN. 191 

turns it immediately blue. Oxonized air irritates the respiratory 
organs, and a minute fraction of a grain kills a rabbit. 

458. If some of the prepared paper be exposed for a few 
minutes to the open air, it will often turn blue, which is supposed 
to be owing to the presence of ozone. The amount of ozone in 
the air is variable, and winds blowing from the sea are said to 
contain more of it than those which sweep over large tracts of 
land. Of its mode of production in nature nothing is known : it 
may be effected by electrical influence. It is probable that it is 
generated on a large scale in the atmosphere, and that it subserves 
a high purpose in the economy of the globe as a purifier of the 
air and hastener of decay. 

459. Theory of Ozone. — There is much unanimity of opinion 
as to the explanation of ozone among those who have most ably 
investigated the subject, and the view has all the more interest as 
it is part of a general chemical doctrine which has lately become 
prominent. 

460. It is well known that bodies when in combination pre- 
sent characters very different from those which they exhibit in 
the free state. It seems, in fact, that few, if any elementary sub- 
stances are actually known to us in their uncombined condition, 
and that what we call the c elements ' are, in reality, compounds 
of at least two atoms of the true element with each other, the 
atoms being probably in different states. Thus hydrogen gas is 

not simply H, but I , or H 2 , or hydride of hydrogen. Chlorine 

Cli 

gas is not CI, but „ I , or chloride of chlorine ; while cyanogen is 

not Q 2 N", but J^. > , or cyanide of cyanogen. According to 

this view the term atom applies to that smallest part of an element 
which can enter into combination, but which is not known in a 
separate form : while the word molecule is used to indicate the 
smallest quantity of any element which can exist in a separate 

state. For instance, N is the atom of nitrogen, ^-> its molecule. 

458. How is it detected in the air ? What winds produce the greatest effect ? 
How is it produced in nature? What purpose does it subserve ? 459. What is 
said of the theory of ozone ? 460. What is probably the state of the so-called 
elements? Give examples. What then is meant by atom t What by molecule ? 



192 INORGANIC CHEMISTRY. 

461. Prof. Brodie maintains that when two particles enter 
into union with each other, it is because they are in different 
states — chemically positive and negative. Substances cannot com- 
bine with each other unless they are in this polar condition, and 
they retain it in combination. Silver is not oxidized by common 
oxygen, because they do not become polar by contact. But if 
silver and oxygen are already combined with other elements, and, 
therefore, in opposite states, they may be made to unite with each 
other. Thus, in chloride of silver, the chlorine is chemically 
negative, and the silver chemically positive ; in oxide of potas- 
sium, the oxygen is chemically negative, and the potassium chem- 
ically positive. If these compounds are brought together, double 
decomposition results, and oxide of silver is formed thus : 

CI Ag __. 01 E 

KO AgO. 
According to this view, ordinary free oxygen is a medium or neu- 
tral body, produced by atoms which are chemically positive and 

+ - 
negative; as O O = 2 , the molecule of free oxygen; while ozone 

is polarized or decomposed oxygen. 

462. Schonbein entertains similar views of the nature of 
cfzone. He says there are two kinds or allotropic modifications 
of active oxygen, standing to each other in the relation of + to — ; 
that is, there is a positively active and a negatively active oxygen 
- — an ozone and antozone, which, on being brought together, neu- 
tralize each other into common or inactive oxygen, according to 

o o 

the equation +0 — 0=0. 

§ III. Hydrogen. 
Sym. H. Equiv. 1. Sp. Gr. 0.0692. 

463. Hydrogen was first described as an element by the Eng- 
lish chemist Cavendish in 1766. It is never found free in nature, 
but exists abundantly in combination, forming one ninth by weight 
of water and a considerable proportion of all organized substances. 

461. What does Prof. Brodie give as the cause of chemical union ? Why will not 
silver unite with common oxygen? How is it in double decomposition? By this 
view what is ozone ? 462. What is Schonbein's view ? 463. When and by whom was 
hydrogen discovered ? How is it found in nature ? What objection is made to its 
name ? 464. How is it generally obtained ? In what ways ? Explain Fig. 175. What 



HYDEOGEN. 193 

The word hydrogen signifies generator of water, but it is strictly 
no more applicable to this element than to oxygen. 

464. Preparation. — Hydrogen is generally obtained by the de- 
composition of water, which is effected in various ways. A cur- 
rent of electricity passed through water liberates both the oxygen 
and hydrogen, when they may be collected separately (212). 
Steam passed through a red-hot gun barrel is decomposed by the 
iron which combines with the oxygen, setting the hydrogen free. 
It is commonly prepared, however, by the action of dilute sul- 
phuric acid upon bits of zinc. The zinc is placed 
in a bottle and covered with water. A cork per- FlG * 1W# 
forated for the insertion of two tubes is then 
tightly fitted to the mouth of the bottle, Fig. 175. 
The tube for admitting the acid dips beneath the 
water ; the other delivers the gas, which is col- 
lected in jars in the same manner as oxygen. 
The water is decomposed by the zinc, which 
unites with its oxygen, forming oxide of zinc, 
while the hydrogen is set free and escapes. The 
sulphuric acid dissolves the oxide of zinc as fast preparing Hydros 
as it is formed, thus maintaining a clean metal- 
lic surface continually in contact with the water. The changes 
are represented by the following equation : 

Zn-f-HO + SOs = ZnO, S0 3 + H. 
The portions first collected are not to be used, as, when mixed 
with air, hydrogen gas is always explosive. 

465. Properties. — As thus prepared, hydrogen has a disagree- 
able odor arising from the impurities of the materials employed ; 
but pure hydrogen is a colorless, tasteless, inodorous gas, very 
slightly soluble in water and very inflammable. All attempts to 
liquefy it, either by pressure or cold, have failed. Dr. Faeaday 
found that it would escape through the joints of apparatus that 
were perfectly tight to other gases ; its atoms must therefore be 
comparatively much smaller. A stream of the gas directed against 
one side of a piece of gold leaf passes through so rapidly that it 
may be ignited on the other side. It is the lightest of all known 
substances, being 16 times lighter than oxygen and 144 times 

are the chemical changes ? Why are not the first portions used ? 465. What are the 
properties of pure hydrogen ? What is said of the smallness of its atoms ? Of its 




194 



INORGANIC CHEMISTRY. 



Fig. 176. 



lighter than air. This adapts it for inflating "balloons, though coal 
gas (which contains hydrogen, and is very light) is generally used 
from its greater cheapness. Owing to its extreme rarity, a hell 
rung in hydrogen is scarcely audible ; and when it is inhaled, the 
voice becomes remarkably shrill. Though pure hydrogen is not 
poisonous, it will not support life, and an animal immersed in it 
soon dies from want of oxygen. 

466. Combustion of Hydrogen. — There is a strong affinity be- 
tween oxygen and hydrogen. If these gases are mixed (2H to 10, 
by bulk), and then ignited, they combine with a violent explosion. 
Soap bubbles, if blown with this mixture from a bag, rise, and if 
fired with a candle, detonate like a pistol. The instantaneous con- 
densation of the gases produces a vacuum, and the sharp report 
is caused by the collision of the particles of air as 
they rush in to fill the void. 

467. Burning bodies are commonly extinguished 
when plunged into hydrogen, although a jet of oxy- 
gen will burn in it. Oxygen and hydrogen burn 
quietly when brought cautiously into contact, emit- 
ting a feeble blue light. Three properties of hydro- 
gen may be shown by a very simple experiment — its 
levity, combustibility, and explosiveness. A jar is 
filled with it, and though held mouth downward, 
it does not escape. If a lighted candle be introduced,'Fig. 176, it is 
extinguished, while the gases burn at the mouth of the jar. If the 
candle is withdrawn, it is relit by the flame at the 
mouth, while, if the jar is reversed, the hydrogen is 
mixed with a little air, and produces a slight explosion. 
468. If hydrogen is generated in a jar and allowed 
to escape through a fine tube, Fig. 17V, into the air, it 
burns, when ignited, with a small, steady flame, giving 
out but little light, though producing intense heat. In 
all cases where hydrogen is burned with oxygen, water 
is the product. If a cold, dry glass is held over the 
Ph c an die! Cal J et > {t is q™kly covered with a film of dew, which 
rapidly increases to drops of water. The gases unite 
to form steam, which then condenses into the liquid state. 




Burning Hydro- 
gen. 



Fig. 177. 




use in balloons ? How is it related to sound ? To life ? 466. How is its affinity for 
oxygen shown ? What causes the explosion ? 467. What is taught by the exper- 
iment, Fig. 176? 468. What is the product when hydrogen is burned? How is 



HYDKOGEN. 



195 



Fig. 178. 




Singing Hydro- 
gen Flame. 



469. Singing Flames. — A common experiment is to lower a 
glass tube over the gas jet, as represented in Fig. 178, when a clear 
musical tone is produced. This is explained by supposing that the 
rapid current of air which rises through the tube 
interrupts the combustion, and, mingling with the 
hydrogen, produces a series of slight explosions in 
such rapid succession as to cause a continuous sound. 
The pitch of the sound varies with the size and 
length of the tube, and with the size of the jet ; and 
a series of tubes and jets may therefore be so grad- 
uated as to give the notes of the musical scale. A 
very pretty effect is produced by introducing the 
flame a short way into the tube, which may be held 
steadily in position by a clamp. No sound is emit- 
ted ; if now the experimenter pitches his voice to 
the proper note, the flame begins to sing in unison. 
A person twenty or thirty feet away, by thus speaking 
to it, causes the jet to start into song — a remarkable 
illustration of the effect of transmitted pulsations. 

470. Combustion of Hydrogen by Condensation. — If a small 
quantity of the solution of the metal platinum be evaporated on 
a piece of writing paper, and the paper burned, the metal remains 
in a state of fine division known as spongy pla- 
tinum. If now a stream of hydrogen be directed 
upon a little ball of platinum sponge, it instantly 
becomes red hot, and remains so as long as the 
current lasts. The metal contains atmospheric 
oxygen condensed within its pores, and by con- 
densing the hydrogen also, their particles are 
brought within the range of affinity, and com- 
bination takes place with the production of heat. 
Dobereixer's lamp is a contrivance for employ- 
ing this principle. The outer glass vessel, a, 
Fig. 179, contains dilute sulphuric acid. The 
inner glass vessel, /, is without a bottom, and Dobereixer's Lamp, 
has suspended within it a piece of zinc. When the acid comes in 
contact with the zinc, hydrogen is immediately generated, and fills 
the vessel, f, pushing down the sulphuric acid so that it is no 

this shown ? 469. How are musical tones produced ? What is the explanation ? 
How is the effect of transmitted pulsations illustrated? 470. How may combus- 



Fig. 179. 




196 INOEGANIC CHEMISTRY. 

longer in contact with the zinc, and the production of gas of 
course stops. On touching the lever, c, a valve is opened, and the 
jet of gas, as it escapes, strikes upon the platinum at cZ, which is 
made red hot. As the gas leaves the vessel, f, the acid again rises 
into contact with the zinc, more hydrogen is set free, and thus the 
effect is constant. 

471. But the porous condition of the metal is not essential to 
this action. Clean slips of platinum or other metals will con- 
dense the gases upon their surface sufficiently to cause rapid com- 
bination. Other bodies also beside hydrogen, as vapors of alcohol 
and ether, may be oxidized by this peculiar surface action. Hy- 
drogen is remarkable among the elements for the enormous amount; 
of chemical energy manifested by a small quantity of matter. Thus 
in combination it perfectly neutralizes 36 times its weight of the 
intense element chlorine, and extinguishes the properties of 125 
times its weight of iodine. 

472. Is Hydrogen a Metal ? — Hydrogen in combination is re- 
placed by metals, and has many analogies with them (707) ; hence 
Dumas and others have supposed that if, like mercurial vapor, it 
could be condensed into a liquid, it would be found to possess a 
metallic nature. But it has been found that hydrogen is also re- 
placed by the strongest anti-metal chlorine, and that its analogies 
with the chlorous elements are as numerous, as strongly marked, 
and as important as with those of the basylous class. We must 
hence regard it as a neutral or intermediate body. 

§ IV. Compounds of Oxygen and Hydrogen. 

WATER. 

(Protoxide of Hydrogen.) Sym, HO. Equiv. 9. Sp. Gr. 1.000. 

473. Of the importance of water in the economy of nature little 
need be said ; it is obvious to all. It is the most abundant sub- 
stance that we know, and it seems as if the whole scheme of na- 
ture were conformed to its properties. Turning to solid ice, or 
exhaling into invisible vapor, its changes of form involve the very 
history of 4he globe (1271). Bising from the ocean, condensed 
upon the land, and flowing back again to the sea, it carries on in 

tion be effected by condensation ? Explain the action of Dobereiner's lamp. 
471. "What illustrations are given of surface condensation ? For what is hy- 



OXYGEN AND HYDKOGEN WATER. 



197 



Fig. 180. 




Fig. 181. 



its circulation the grand processes of the world. Composing fonr 
fifths the weight of the vegetable kingdom and three fourths that 
of the animal, it is the first condition of all organization, and by 
innumerable transformations and decompositions, it is essential to 
the continuance of organic life. 

474. Nor is it less indispensable in the laboratory of the 
chemist. It is the ready, invaluable medium of a 
thousand operations ; it is involved in nearly every 
chemical process ; in fact, the chemistry of water, 
theoretical and practical, might fitly be taken to 
represent the present state of the science. 

475. Composition. — Water is a compound of 
8 parts by weight of oxygen to 1 of hydrygen, or Decomposing Wa- 
by bulk 1 of oxygen to 2 of hydrogen. Its com- 
position may be proved in many ways, but one of 
the most simple is to throw a little metallic potas- 
sium upon its surface. The metal instantly decom- 
poses it, seizing upon the oxygen with such vio- 
lence as to produce vivid combustion, Fig. 180 ; 
the water seems set on fire. 

476. But the composition of water may be shown 
in the most perfect manner by sending an electric 
current through a vessel of it, Fig. 181, as already 
described (212). The gases are set free in the ex- 
act proportions given above, and if mixed together 
and ignited, they combine with a loud and sharp 
explosion, the product being pure water. The 
composition of water is thus demonstrated by both analysis and 
synthesis. An arrangement for exploding gases to determine the 
amount of their condensation is called a Eudiometer. 

4:11. Water is not only decomposed as stated above, but also 
by sodium, iron, zinc, and many other metals ; in fact, they are 
classified according to their degrees of power in this respect. In 
numberless operations of chemistry, the elements of water are 
separated and reunited, and the same thing is going on perpetually 
in vegetable and animal organisms. 




Electro-Decom- 
position. 



drogen remarkable ? 472. How must we regard it as a neutral body ? 473. How 
are the properties of water related to the scheme of nature ? 474. How does the 
chemist regard it? 475. "What is its composition? What simple experiment 
proves it ? 476. What does Fig. 181 represent ? What is an Eudiometer ? 477. How 



198 



INORGANIC CHEMISTRY. 



478. General Properties. — "Water, as is well known, is a trans- 
parent, tasteless, inodorous liquid. It is but very slightly con- 
densible ; according to Eegnault, being compressed 1-47 millionth 
of its bulk for each atmosphere of pressure (563), and is perfectly 
elastic, as it regains its full dimensions when the pressure is 
removed. It evaporates at all temperatures ; boils at 212°, and 
freezes at 32°. At 60°, a cubic inch of pure water. weighs 
252.456 grains, which is 815 times the weight of an equal bulk of 
air. An imperial gallon weighs 70,000 grains, or just 10 lbs. 
The American standard gallon weighs 58,972 grains of pure dis- 
tilled water at the maximum density (484). In thin sheets, water 
is colorless, but when viewed in thick masses, it has a decided 
tint. Light passed through fifteen feet of pure distilled water, 
emerges of a bright and delicate blue-green, and by augmenting 
the thickness, the color is deepened. Natural waters are discol- 
ored by various impurities in different places. 

479. Water Purified by Freezing. — During freezing, the sub- 
stances dissolved in water are expelled; hence the ice of sea 

Fig. 182. water (as is well known to 

sailors), when melted, be- 
comes fresh water. For the 
rf\"< same reason, water from 
j<^>o melted ice contains no air, 
VU ^ nor gas — fish cannot live in 
it. Ice melted under spirits 
of turpentine, where no air 
can get access to it, produces 
water so cohesive, that it can 
be heated far beyond its boil- 
ing point, when it bursts into 
explosive ebullition (288). 
480. Liquid Flowers in 




Forms of Ice Flowers. (Ttndall.) 



Ice. — When a ray from the sun or an electric lamp is made to 
pass through a block of pure ice, a portion of the heat is arrested, 
and must, of course, produce change. As it cannot warm the ice, it 
melts it. But the ice particles return to the liquid state in definite 
order, and, upon examining it with a magnifier, the ice is seen to 
be filled with beautiful flower-like figures, such as are shown in 



are metals classified ? What is everywhere occurring ? 478. What are the general 



OXYGEN AND HYDROGEN — WATER. 199 

Fig. 182. These consist of water, but as the liquid formed cannot 
quite fill the space of the melted ice (484), there occurs a little 
vacuum, which looks like a globule of burnished silver in the 
centre of the flower.* 

481. Snow Crystals. — The aqueous vapor of the atmosphere, 
condensed by cold in winter, or at great heights in summer, 
assumes the most beautiful crystalline forms — those of snow 
flakes. Perfect snow flakes are six-sided stars, which shoot out an 
infinity of delicate needles, all diverging from each other at an 
angle of 60°. These frozen blossoms, as they have been aptly 
termed, are seen in an endless variety of most exquisite forms, a 
few of which are shown in Fig. 183. 

482. The great specific heat of water (274) is a powerful 
agency in controlling climate. It is four times greater than that 
of air; that is, a pound of water in cooling one degree, would 
warm four pounds of air one degree. But as water is 770 times 
heavier than air, it is obvious that a cubic foot of water in cooling 
one degree, would warm four times 770 cubic feet of air, or 3,080 
cubic feet one degree. Hence, the vast amount of heat stored up 
in oceans and lakes, being gradually imparted to the air during 
winter, modifies the severity of the cold, and explains the fact 
that island winters are less severe than those of continents or 
inland places. 

483. The very stability of nature seems to depend upon this 
quality of the earth's aqueous element. If the watery masses of 



* Prof. Ttndall, -who has advanced these "beautiful researches, thus eloquently 
discourses on this property of ice : ' To many persons here present, this block of ice 
may seem of no more interest and beauty than a block of glass ; but, in the estimation 
of science, it bears the same relation to glass that an oratorio of Handel does to the 
cries of a market place. The ice is music, the glass is noise ; the ice is order, the 
glass is confusion. In the glass, molecular forces constitute an inextricably entan- 
gled skein ; in the ice they are woven to a symmetric web, the miraculous textures 
of which I will now try to reveal.— How shall I dissect this ice ? In the solar 
beam, — or, failing that, in the beam of an electric lamp, we have an anatomist 
competent to perform this work. It shall pull the crystal edifice to pieces, by 
accurately reversing the order of its architecture. Silently and symmetrically the 
crystallizing force builds up the atoms, silently and symmetrically the electric 
beam will take them down ! Probably few here present were aware of the beauty 
latent in a block of common ice. And only think of lavish nature operating thus 
throughout the world ! Every atom of solid ice which sheets the frozen lakes of 
the North has been fixed according to this law. Nature ' lays her beam in music,' 
and it is the function of science to purify our organs, so as to enable us to hear 
the strain.' (Tyndall's Lectures on Heat.) 

properties of water? 479. What is the effect of freezing upon water? What is 
said of water from melted ice? 480. How are liquid flowers produced in ice? 
481. What are snow flakes ? Describe them. 4S2. How does the great specific heat 



200 



INORGANIC CHEMISTRY. 
Fig. 183. 




Forms of Snow Flakes. (Glaisher.) 

the globe, and that large proportion of it contained in onr own 
bodies, lost and acquired heat as promptly as mercury, the varia- 
tions in temperature would be inconceivably more rapid than 
now ; the inconstant seas would freeze and thaw with the great- 
est facility, while the slightest changes of weather would send 
their fatal undulations through all living systems. But now the 
large amount of heat accumulated in bodies of water during sum- 
mer, is given out at a slow and measured rate ; the climate is 
tempered, and the transitions from heat to cold are gradual and 
moderated. 

484. Unequal Expansion of Water.— This liquid contracts as 
its temperature falls from the boiling point till it reaches 39°, 
when it remains stationary for a time. It then begins to expand, 
and in cooling through 7 degrees to the freezing point, it reaches 
the same volume it had at 48°. The point of greatest contraction 
is called the maximum density of water. This fact is of great 
importance in nature. If water continued to contract as it cooled, 
it would be denser and heavier at the freezing point, and, conse- 
quently, sink. Lakes and rivers would then begin to freeze at the 



of water affect climate ? 483. What is said of the importance of this quality in 
nature ? 484. What is said of the unequal expansion of water? If water contin- 



OXYGEN AND HYDROGEN — WATER. 201 

bottom first, and, in the course of the winter, would become solid 
masses of ice ; while the length of time required to thaw them 
would greatly prolong the cold season. But as the surface stratum 
of water approaches the freezing point and freezes, it expands, 
and, becoming lighter, floats, and thus the coldest water and ice 
are kept at the surface, where, as they are almost perfect non- 
conductors of heat, they protect the mass of water below from 
the cold above. In freezing, water expands with such power as 
to burst the strongest vessels. Percolating through the minute 
crevices and fissures of rocks in summer, it freezes in winter, and 
expands with a force which breaks the solid stones, crumbling 
them into soil fit for the support of vegetable life. 

485. The property of water by which these effects are pro- 
duced, has been regarded as exceptional, but this is not the case. 
Bismuth and other metals in the act of solidifying also expand. 
Nor is this effect, probably, any rear exception to the law of 
expansion by heat. Another force is evidently brought into play 
which masks the regular action of the heat. Clay contracts by 
heat, but it is due to the shrinkage from loss of water, which 
happens to be greater than the expansion produced by heat. So 
there can be little question that the play of crystalline forces 
interferes with the result. As liquids crystallize, on approaching 
solidification, there is a rearrangement of the molecules with 
enlarged interspaces and consequent expansion. 

486. Atomic Constitution of Water. — There are various rea- 
sons for supposing that the composition of water, instead of being 
HO, is H 2 2 . First, the heat-absorbing power of aqueous vapor 
is high, like that of the complex-atomed gases (346). Second, 
when H and combine to form water, there is so great a loss of 
mobility as to suggest that the atoms, instead of uniting in simple 
pairs, combine into higher and more sluggishly moving groups. 
Third, the excessive amount of heat that results from their com- 
bination, suggests a great amount of atomic motion ; and, fourthly, 
this idea is countenanced by the behavior of water in expanding 
by cold, as it approaches the freezing point, as just noticed. 

487. Water of Combination. — Water unites with bodies with 
three degrees of intensity. In its closest union it forms com- 

ned to contract as it cooled, what would follow ? What instances are given of the 
force with which water expands in freezing? 485. Is this property of water excep- 
tional ? What is the probable explanation ? 486. What reasons are given for sup- 
9* 



202 INORGANIC CHEMISTRY. 

pounds known as hydrates, where the water is so intimately 
combined that a heat approaching to redness is required to sepa- 
rate it; slaked lime is such a hydrate. Secondly, it combines 
with crystalline bodies in definite proportions. This is termed the 
water of crystallization, to distinguish it from the water of hydra- 
tion. The formula for crystallized sulphate of magnesia, for 
example, represents both states of combined water : 

MgO,S0 3 , HO + 6Aq. 

Thirdly, water combines in all proportions, in a still more loose, 
chemico-mechanical way, as a solvent. 

488. Water is perfectly neutral, manifesting neither acid nor 
basic properties, and yet it is capable of playing the part of both. 
It combines powerfully with acids, and, acting the part of a base, 
is known as basic water. Hydrated sulphuric acid, HO, S0 3 , is 
thus a sulphate of water, mor can the water be expelled from the 
combination, except by a more powerful base. It combines also 
with bases, potash for example, playing the part of an acid, and 
can only be displaced by a stronger acid. 

489. Solvent Power of Water. — Its perfect neutrality enables 
it to take on the properties of other substances, and hence with 
equal facility it becomes sweet, sour, salt, astringent, bitter, or 
poisonous, according as the bodies it dissolves possess these prop- 
erties. This solvent power is variable upon different substances, 
and at different temperatures. Thus, a pound of cold water will 
dissolve two pounds of sugar, while it will only take up two 
ounces of common salt, two and a half of alum, and eight grains 
of lime. Heat generally increases the solvent power of water ; 
thus boiling water will dissolve 17 times as much saltpetre as ice 
water. But there are exceptions to this rule ; ice water dissolves 
twice as much lime as boiling water. 

490. The Water Atmosphere. — Water dissolves gases in the 
most diverse proportion, taking up 700 times its bulk of ammonia ; 
its own bulk of carbonic acid ; ^ its bulk of oxygen, and still less 
of nitrogen. There is, therefore, an atmosphere diffused through- 
out all natural waters, which is richer in oxygen than common 

posing that the atomic constitution of water is H 2 2 ? 487. "What are hydrates? 
What is meant by water of crystallization? How else does water combine with 
bodies ? 488. What is basic water ? Examples. When does it play the part of an 
acid ? 489. How does the solvent power of water vary ? What is the effect of heat 



OXYGEN AND HYDROGEN — WATER. 203 

air, and hence better adapted for supporting the life of aquatic 
animals. The gases absorbed by water give it a brisk, agree- 
able flavor, and if driven off by boiling, the liquid becomes 
insipid. 

491. Different Kinds of Water, — As water dissolves a little 
of nearly every substance with which it comes in contact, it is 
never found perfectly pure in nature. Hence there are many 
varieties of natural water, as spring, river, rain, sea, and mineral 
water. Eain falling in the country, away from habitations, and 
after a protracted wet season, is the purest water nature produces, 
as it is contaminated only with the natural gases of the atmo- 
sphere. In cities, as it falls through the air, it absorbs the various 
organic and gaseous impurities with which it comes in contact, 
and, flowing over the roofs of houses, carries down the deposited 
soot, dust, &c. Water from melted snow is purer than rain water, 
as it descends through the air in a solid form, incapable of absorb- 
ing gases. 

492. Mineral Impurities. — Eain water, which has filtered 
through the porous soil and strata of the earth, dissolves snch 
portion of its soluble materials as it meets with, and carries them 
down to the lower levels, so that they may ultimately collect in 
the sea. The amount of mineral water thus dissolved is remark- 
ably various. The water of the Eiver Loka in Sweden, which 
flows over insoluble granite, contains only ■£$ of a grain of mineral 
matter in an imperial gallon. Common well-waters and spring 
and mineral waters contain from 5 to 60 grains per gallon. Sea 
water contains 2,600 grains to the gallon; and that from some 
parts of the Dead Sea or the Great Salt Lake of Utah, as much as 
20,000 grs. to the gallon — 400,000 times as much as the Loka 
water. 

493. The mineral impurities of well and spring water are 
chiefly lime, magnesia, soda, and oxide of iron, combined with 
carbonic and sulphuric acids, which form carbonates, sulphates, 
and common salt. The most universal ingredients, however, are 
carbonate and sulphate of lime. Carbonate of lime, or limestone, 

upon it ? 490. How much ammonia does water dissolve ? How is it with other 
gases ? "What is the effect of the dissolved gases upon the water ? 491. Why are 
there so many varieties of natural water ? How do different localities cause waters 
to differ? What are the purest waters? 492. How does water ohtain its mineral 
impurities? Give instances of their variable quantity. 493. What are the chief 



204 INORGANIC CHEMISTRY. 

is not soluble in pure, water, but dissolves in water containing 
free carbonic acid, which is present in most natural waters. 

494. Sea Water. — The solid constituents of sea water amount 
to about 3 1 per cent, of its weight, or nearly half an ounce to the 
pound. Its saltness is a necessary result of the circulation of 
matter. Bivers flow into the ocean with their saline constituents, 
while- the water which evaporates from the sea is nearly pure. 
The ocean, therefore, is the great depository of everything that 
water can dissolve and carry down from the surface of the conti- 
nents, and, as there is no channel for their escape, they constantly 
accumulate. The continuance of this process for numberless ages 
accounts for the present saline condition of the oceans. In the 
same way all lakes into which rivers flow, and which have no 
outlet, are salt lakes. The Dead Sea, for example, is situated at 
the bottom of an immense basin — several hundred feet lower than 
the Mediterranean, and has no outlet. The Jordan flows into it, 
bearing 75 grains of saline matter to the gallon, and there is no 
escape but by evaporation ; hence its excessive saltness. 

495. Mineral Waters are usually those of springs which con- 
tain a considerable amount of various saline matters. Those 
abounding in salts of iron are called chalybeate, or ferruginous 
waters. If the waters are brisk and sparkling, carbonic acid gas 
is present, and they are termed carbonated, or acidulous waters. 
If the active ingredient be sulphur, the spring is called sul- 
phurous. The water of the celebrated Congress Spring, at Sara- 
toga, contains the following ingredients in a gallon : 



Chloride of Sodium, .... 


. 390,246 grains. 


Iodide of Sodium, and Bromide of Potassium, 


6,000 " 


Carbonate of Soda, .... 


9,213 " 


Carbonate of Magnesia, .... 


100,941 " 


Carbonate of Lime, .... 


. 103,416 " 


Carbonate of Iron, ..... 


1,000 " 


Silex and Alumina, .... 


1,036 " 


Total solid contents, . _ . 


611,852 grains. 



496. Hard Water. — "Water derives its quality of hardness from 
the presence of salts of lime, chiefly the sulphates ; a single grain 
of which will convert 2,000 grains of soft into hard water. "When 



mineral ingredients of well and spring water? To what does carbonate of lime 
owe its solubility? 494. Explain the cause of the saline condition of the ocean. 
I 



OXYGEN AND HYDROGEN — WATE 205 

common soap is put into hard water, instead of dissolving in it, as 
it does in soft water, it curdles, or is decomposed, and a new soap 
is formed which contains lime instead of potash or soda. This 
new soap will not dissolve, and may often be seen on the surface 
in the form of a greasy scum. It adheres to whatever is washed 
in it, and gives to the touch the unpleasant sensation of hardness. 
To test this quality of water, dissolve a little soap in alcohol, and 
place a few drops of it in the water to be examined. If it remains 
clear, the water is perfectly soft ; if it becomes turbid or opaque, 
the water is ranked as hard. Hard water is a less perfect solvent 
than soft water, and is, therefore, inferior to it for culinary 
purposes. 

497. Organic Impurities of Water. — From the dust and insects 
of the air, drainage of residences, the decay of leaves and animals, 
and a multitude of other causes, water is liable to organic con- 
taminations. These may be either mechanically suspended, or 
dissolved in it. "Water containing dissolved organic matter is 
highly dangerous to health, and should be carefully avoided. 
Solution of permanganate of potash is decomposed and decolor- 
ized by it, and, therefore, water which discharges the color from 
much of this reagent should be viewed with suspicion. 

498. Organic impurities, if suspended mechanically in water, 
are noxious, but they are generally attended by a correction more 
or less efficient in the shape of animalcule, which feed upon them. 
These living inhabitants are never found in freshly fallen rain 
water, caught at a distance from houses, nor in spring or well 
water; but they more or less abound in cistern and reservoir, 
marsh, pond, and river waters. The Kiver Thames has been 
found to contain 23 different species of these organisms. They 
make a frightful appearance when exhibited by the oxy-hydrogen 
microscope, but they perform an invaluable service in consuming 
dead organic matter, and reducing it to its ultimate and innocent 
constituents — carbonic acid, water and ammonia. 

499. Purification of Water. — The best method of purifying 
water is by distillation; to render it perfectly pure, it must be 
redistilled at a low temperature, in silver vessels. By filtration 
through sand, crushed charcoal, or other closely porous media, 

How is it with the Dead Sea ? 495. How are mineral waters classed ? 496. What 
is hard water? Its action on soap? Its test? 497. Whence come its organic 
impurities? Why should such water bo avoided? How may we test it? 



200 INORGANIC CHEMISTRY. 

water may be deprived of suspended impurities, and of all living 
beings. Boiling kills all animals and vegetables, expels gases, and 
precipitates carbonate of lime, which constitutes the fur or crust 
often seen lining tea kettles and boilers. Alum (two or three 
grains to the quart) cleanses muddy or turbid water. It is de- 
composed by carbonate of lime, and the alumina set free carries 
down the impurities mechanically ; but the sulphuric acid of the 
alum, combining with the lime, forms sulphate of lime, and makes 
the water harder than before. The alkalies, potash or soda, 
soften water by decomposing and precipitating the earthy salts. 

500. Peroxide of Hydrogen, H0 2 , has been produced by the 
chemist, and called oxidated water. It is a transparent, sirupy 
liquid, with an astringent taste, a decided odor, and possesses active 
bleaching properties. It is very unstable in composition ; the mere 
contact of various substances causing it to decompose explosively. 



§ Y. Nitrogen and its Compounds. 

NITROGEN. 

Sym. K Uquiv. 14. Sp. gr. 0.971. 

501. This gas was discovered by Rutheeford in 1772. It is 
very extensively diffused in nature, forming about four fifths of 
the atmosphere, in which it plays the important part of diluting 
the oxygen, and adapting it to the conditions of life. It is an im- 
portant element of the vegetable kingdom, entering in consider- 
able quantity into many of its compounds. It is supplied to plants 
by ammonia and nitric acid, and exerts a very favorable influence 
upon the growth of vegetation. Our food is largely composed of 
nitrogen, and it forms 16 per cent, of the tissues of the animal 
body. It is an essential part of many powerful medicines, as 
quinine and morphia, and of some of the most dangerous poisons, 
as strychnine and prussic acid. Nitrogen is not found in any of 
the mineral formations of the earth's crust, except in some varieties 
of coal. 

502. Preparation. — It is called nitrogen, generator of nitre, 

498. What is said of animalcula in water ? 499. Mention the various modes of 
cleansing water ? 500. What are the composition and properties of peroxide of 
hydrogen? 501. What are the proportion and office of nitrogen in the atmo- 



NITROGEN AND ITS COMPOUNDS. 



207 



Fig. 184. 




Fig. 185. 



because it exists in that substance, and may be produced from it. 
It is most commonly prepared by withdrawing oxygen from a por- 
tion of air. A small bit of phosphorus is placed 
in a little cup and floated on the water in a pneu- 
matic trough. It is then set on fire and a jar 
placed over it, as in Fig. 184. The phosphorus 
takes the oxygen, forming phosphoric acid, which 
fills the jar with a white vapor ; but this is soon 
absorbed by the water, and nitrogen alone is left, 
the water rising to occupy the space of the van- Preparing Nitrogen, 
ished oxygen. One hundred volumes of water dissolve about two 
and a half volumes of nitrogen. 

503. Properties. — Nitrogen is a transparent gas without taste 
or color, and has never been condensed into a liquid. It is remark- 
able for chemical inertness, and can only be combined with other 
substances by indirect means. Owing to its weak affinity for the 
other elements, it forms very unstable compounds, and on the 
slightest occasion escapes from them in its gaseous form. It sup- 
ports neither combustion nor 
respiration : a lighted taper in- 
troduced into it is immediately 
quenched, and animals placed 
in it quickly die, not from its 
poisonous action, but from lack 
of oxygen. Hence it was for- 
merly called azote) or life de- 
stroyer. 

504. Nitrous Oxide, NO. — 
Oxygen combines with nitro- 
gen to form a series of five 
compounds, remarkable as illustrating in a perfect manner the 
law of multiple combination. (See Chart.) The first in the series 
is protoxide of nitrogen, or nitrous oxide, called also, from its pecu- 
liar effects when respired, laughing gas, or exhilarating gas. It is 
prepared from nitrate of ammonia by moderately heating this salt 
in a flask. The gas escapes through a tube, and is collected in jars 
over water, Fig. 185. Four ounces of the salt produce one cubic 

sphere ? How is it supplied to plants? "Where else is it found ? 502. Why is it 
called nitrogen? How is it prepared? 503. What are its properties ? Why are 
its compounds unstable ? Why was it called azote 7 504. For what is the nitrogen 




Making Nitrous Oxide. 



208 INORGANIC CHEMISTRY. 

foot of the gas. It should be allowed to stand for some time over 
water, to absorb any nitrous acid that may chance to be formed. 
The chemical change may be thus represented : 

H 3 irao, ]sro 5 = 4HO + 2sro. 

One atom of nitrate of ammonia (or nitrate of oxide of ammonium), 
yields four atoms of water and two of protoxide of nitrogen. 

505. Properties. — Nitrous oxide is a neutral, colorless, trans- 
parent gas, of a slightly sweetish taste, and very soluble in water 
— cold water absorbing about three fourths of its volume. Sp. gr. 
1.527. It is an active supporter of combustion, relighting a glow- 
ing candle when plunged into it, and intensifying the combustion 
of phosphorus almost equally with pure oxygen. A pressure of 
50 atmospheres at 45° condenses it into a clear liquid which boils 
at about 1126°, and may be frozen at about — 150°. 

506. When breathed this gas produces a transient intoxication, 
attended sometimes with an irresistible propensity to laughter, 
and at others with a tendency to muscular exertion, individuals 
being variously affected according to temperament. The gas 
should be pure, and even then the experiment is not a safe one 
where there is an over-active circulation in the brain. These 
effects may undoubtedly be ascribed to an augmented oxidation, 
produced in the system by the gas. When taken into the lungs, 
being far more soluble than oxygen, it is rapidly dissolved in the 
blood, and quickly diffused throughout the body. 

507. Nitric Oxide E"0 2 , (Beutoxide of Nitrogen), is formed by 
the action of nitric acid upon slips of copper in a similar way to 
the production of hydrogen, Fig. 175. A portion of the nitric 
acid is decomposed, giving up three atoms of its oxygen to the 
copper, M) 2 escaping. The oxide of copper thus produced unites 
with a portion of the nitric acid, forming nitrate of copper which 
gives a blue color to the solution. 

3Cu + 4IST05 = 3CuO, M) 5 + N0 2 . 
Nitric oxide is a colorless, irrespirable gas that has not been lique- 
fied, and which extinguishes most burning bodies. Brought in con- 
tact with air, it acquires oxygen and produces red fumes of N0 4 . 

and oxygen group of compounds remarkable ? How is nitrous oxide prepared ? 
Explain the chemical changes. 505. State its properties. 506. What are its 
effects when breathed ? How is this action accounted for ? 507. What is the com- 
position of nitric oxide ? How is it produced ? Give the equation. What are its 



OTTROGEN AND ITS COMPOUNDS. 



209 



508. Nitrous Acid, ]ST0 3 , formerly Eyponitrous Acid. — This 
is a thin mobile liquid, producing an orange-red vapor, and form- 
ing a class of salts known as the nitrites. Hyponilric Acid (Pe- 
roxide of Nitrogen), N0 4 , is an orange-colored fluid with a cherry- 
red vapor. It boils at 82°, and solidifies at 8°. 

509. Nitric Acid (Aqua Fortis), K0 5 , is a colorless liquid (sp. 
gr. 1.521) with an intensely sour taste. It smokes when exposed 
to the air, and is partially decomposed by the action of light, hy- 
ponitric acid be- 



ing formed, which 
gives it a yellow 
color. It unites 
with bases form- 
ing an extensive 
series of salts — the 
nitrates — which 
are all soluble in 
water ; hence, ni- 
tric acid cannot be 
precipitated. It is 



Fig. 186. 




Preparing Nitric Acid. 



obtained by decomposition of its salts. Equal weights of nitrate 
of potash and sulphuric acid are placed in a glass retort, which is 
supplied with a receiver B, kept cool by cold water flowing over 
it from the tube *, by means of a netting, Fig. 186. "With the 
application of heat, the nitrate is decomposed, and the acid distils 
over into the receiver. The change is thus shown : 

(KO, M) 5 ) + 2(HO, S0 3 ) = (EO, HO, 2S0 3 ) 4- (HO, N0 5 ). 

That is, one atom of nitrate of potash and two of sulphuric acid, 
furnish one atom of bi-sulphate of potash and one of hydrated ni- 
tric acid. 

510. Nitric acid stains the skin, nails, and many other animal 
substances of a yellow color, and is therefore used to produce yel- 
low patterns upon woollen fabrics. It is also employed for etching 
on copper, for assaying or testing metals, and as a solvent for tin 
by dyers and calico printers. In consequence of its large propor- 
tion of oxygen, it corrodes the metals with great energy, and 

properties? 508. "What is nitrous acid? Hyponitric acid? 509. What are the 
properties and composition of nitric acid ? Why can it not be precipitated ? How 
is it obtained ? Explain the reaction. 510. For what is it used ? What of its 



210 INORGANIC CHEMISTRY. 

hence is the most powerful of oxidizing agents. It ignites pow- 
dered charcoal and oil of turpentine, and oxidizes phosphorus so 
rapidly as to produce an explosion. 

511. This acid is found in nature in combination with potash, 
soda, or lime in the soil of various localities ; with potash it con- 
stitutes the saltpetre of commerce. It occurs also in small 
quantity in rain water, especially after thunder storms, and 
is supposed by some to be produced by lightning, which com- 
bines the gaseous nitrogen and oxygen. Others suppose it to 
be produced by the oxidation of ammonia which always exists 
in the air. 

512. Ammonia, H 3 N" (Ammonium, H 4 $T*). This is the only 
known compound of nitrogen and hydrogen. They do not 
combine when mixed or heated, but only in the nascent state. 
Ammonia is therefore a constant product of the decomposition of 
organic substances which contain nitrogen. It is produced from 
the destructive distillation of horns and hoofs, which are rich in 
nitrogeD, but the chief source of commercial ammonia is the liquor 
of the gas works. The gas is conveniently obtained by heating 

, equal parts of newly slaked lime and dry powdered sal ammoniac 

F in a glass. The lime takes the chlorohydric acid, 

j— s forming chloride of calcium, while gaseous ammonia 
fl$h is set free. The change may be thus shown : 

IW HslST, HC1 + OaO = CaCl, HO + H s tf . 

II The gas may be collected in jars in the pneumatic 

W trough, but it must be over mercury, as water ab- 

/ \ sorbs it. It is, however, more convenient to pro- 

A\ cure it by what is called the method of displacement 

'(Rlfl ^^ e ^ as g enerate( l m tne l° w e r vessel, Fig. 187, be- 
^jJIIJpl' ing lighter than the air, accumulates in the upper 
Producing Am- portion of the inverted jar, displacing the air and ex- 
moma. pelling it downward. 

513. Properties. — Ammonia is a colorless, irrespirable gas of 
a pungent, caustic taste, lighter than air (sp. gr. 0.59), and possesses 
strong alkaline properties, changing vegetable blues to green and 
yellows to brown. It neutralizes acids and forms definite salts. 

oxidizing power? 511. How is it found in nature ? 512. What is the composition 
of ammonia? When only is it formed ? What is its chief source ? How may it 
be obtained ? How best collected ? 513. What are the properties of ammonia ? 
* See page 288. 



NITROGEN AND ITS COMPOUNDS. 



211 



Fig. 188. 




Testing Ammonia. 



Being a gas, it is called volatile alkali, to distinguish it from those 
which are fixed or solid. From the circumstance that it was 
derived from the horns of harts, it was called spirits of harts- 
horn, Ammonia is recognized by its odor. If a rod dipped 
in chlorohydric acid he brought near a source of ammonia, a 
white cloud is produced by the union of the two in visible gases, 
Fig. 188. 

514. Ammonia is used medicinally in various 
ways. It is administered internally as a stimulant, 
and applied externally as a counter irritant. Mixed 
with olive oil, it forms 'volatile liniment It is the 
best antidote to prussic acid, but in large doses it is 
poisonous. It is of many uses to the chemist. 

515. Solution of Ammonia. — Ammonia is rap- 
idly absorbed by water which will take up TOO times its volume of it, 
forming the aqua-ammonia of commerce. This is best prepared by 
evolving the gas from slaked lime and sal ammoniac, and passing it 
through a series of bottles. In making solutions of the absorbable 
ga#es several difficulties have to be guarded against. The action 
in the evolution flask is liable to various interruptions, while the 
water present in the apparatus rapidly absorbs the gas. This 
creates a partial vacuum, and the consequence is, that the water 
in the jar flows back into 
the flask, thus putting an end 
to the process ; also, if the gas 
is generated faster than it is ab- 
sorbed, there arises the danger 
of an explosion, unless there is 
a free outlet to the apparatus. 
These dangers are obviated by 
the arrangement known as 
Woulfe's Bottles, Fig. 189. 

516. The flask in which the 
gas is generated is provided 
with a safety tube which serves 
both as a means of introducing^ a liquid and as a protection against 
the above mentioned accidents. When the liquid is poured in, a 



Fig. 189. 







Woulfe's Bottles. 



514. What are some of its uses ? 515. Explain the process for forming aqua-ammo- 
nia ? What trouble is to be guarded against ? 516. By what means ? 517. What 



212 INORGANIC CHEMISTRY. 

portion of it is retained in the bend of the tube, acting there as a 
valve to prevent the access of air to the flask. Each bottle has 
an upright tube in the middle neck which acts as a safety tube, 
allowing the air in case of a vacuum to pass in, or the liquid to 
flow out, if the pressure of the gas becomes too great. The other 
tubes serve to connect the bottles with the flask and with each 
other. 

517. Cold saturated aqua ammonia is lighter than water, boils 
at 130*, and freezes at — i0\ It is a colorless liquid with a pungent 
odor and strong alkaline taste. It is much used by chemists, and 
affords the best means of procuring ammonia, as the gas is readily 
expelled by heat. 

§VL Carbon. 

w 
Sym. 0. JZquiv. 8. Sp. Gr. (Diamond), 3.52. (Vapor), 0.829. 

518. Carbon, from the Latin carlo, coal, is the name applied 
to the solid element of organic bodies with which we are familiar 
in the various forms of charcoal, mineral coal, lampblack, 4cc, 
It is on every account a most interesting element, and plays a very 
important part in the operations of nature. Carbon has three 
well marked allotropic forms — the diamond, graphite, and char- 
coal. 

519. Properties of the Diamond.— The purest form of carbon 
is the diamond — a very extraordinary kind of matter. It is a crys- 
tal the most brilliant and precious of gems, and the hardest body 
known. Diamonds are found in the earth in various places, 
usually in the form of rounded pebbles covered with a brownish 
crust. Of their mode of production nothing whatever is known. 
The finest specimens are perfectly colorless and limpid, but 
they are also of various colors. The diamond has a very high re- 
fractive and dispersive power by which it flashes the most varied 
and vivid colors of light. It is a non-conductor of electricity, and 
resists the action of all known chemical substances. 

520. Combustibility. — The diamond remains unchanged at a 
very high degree of heat ; but if made red-hot and carried into 
pure oxygen, it burns with a steady glow, like a little star, the 

are the properties of aqua ammonia ? 518. "What is carbon ? What are its three 
allotropic forms ? 519. "What is the diamond ? How is it formed ? Its properties 1 



CARBON. 



213 



Fi<?. 190. 




product being carbonic acid. From its high refractive power, re- 
sembling in this respect organic substances (315), Newton pre- 
dicted that it would prove not only combustible, but of organic 
origin. This view seems to be supported by the fact that the 
crystal on being burned leaves a trace of ash in the form of a cel- 
lular net work. In the flame of the voltaic arc, the diamond be- 
comes white-hot, swells up, and is converted into a black coke- 
like mass. 

521. Uses. — Being a powerful refractor of light, the diamond 
has been sometimes employed for the lenses of microscopes, but it 
is chiefly used for cutting glass and drilling apertures through 
other gems. Diamond crystals are in the form 
of a regular octohedron, but their faces are 
often a little convex, as shown in the Fig. 190. 
Only the natural faces of the crystal can be 
used for cutting glass, and the curved edges 
are best. Angles obtained by cleavage pro- 
duce only a rough scratch, like quartz. Though 
the fissure made by the diamond in cutting glass 
is not more than the ^\- Q of an inch in depth, 
yet with a slight pressure on each side or a 
blow, it determines the course of the fracture 
through a very thick plate. 

522. Diamond Cutting. — Diamonds are so 
hard that they can only be cut or wrought by 
means of diamond powder. This fine dust is 
mixed with olive oil and spread upon a plate 
which is made to revolve two or three thou- 
sand times in a minnte. The gem is soldered 
to an arm and pressed against the revolving 
disc by means of weights. In this way the 
diamond is cut into three forms — the brilliant, 
the rose, and the table, as shown by the ac- 
companying figures. The brilliant is cut with 
a plane or table at the top, surrounded with facets. It is also cut 
with facets below, which are made at such angles to those above 
that the most perfect reflection is produced. The brilliant, there- 



Diamond Crystal. 



Fig. 191. 




Brilliant. 



Fig. 192. 




Rose Diamond. 



Fig. 193. 



Table Diamond. 



520, How may it be burned? Why has it been regarded as of vegetable origin? 

521. Its uses ? In cutting glass ? 522. How are diamonds cut ? Describe the bril- 



214 



INORGANIC CHEMISTRY. 



Fig. 194. 



fore, has the finest effect, but requires the sacrifice of the largest 
portion of the gem. A brilliant cut diamond is esteemed equal in 
value to a rough one of twice the weight, added to the cost of 
working it. The rose is cut into a hemispherical form with a 
pointed summit and 24 facets : it is flat beneath. Table diamonds 
are made from thinner specimens. 

523. Value of Diamonds. — The weight and value of diamonds 
are reckoned by carats of four grains each. The average value of a 
perfectly cut diamond weighing one carat is $40. They increase 
in value, not in proportion to their weight, but to the square 
of their weight. The value of three dia- 
monds weighing 1, 2, and 3 carats is as 1, 
4, and 9. This rate of valuation, how- 
ever, only applies to those of moderate 
size, as it would render the price of large 
diamonds so enormous as to place them 
beyond the reach of even the wealthiest. 
524. Of the largest, or, first class dia- 
monds, there are but few ; perhaps less 
than a score altogether. These have been 
so coveted by princes as to have figured 
quite prominently in oriental politics and diplomacy. Fig. 194 
represents a diamond brought from India by a Mr. Pitt, and sold 




The Pitt Diamond. 



Fig. 195. 



Fig. 196. 




Koh-i-noor, before cutting {side view). After cutting {upper face). 

to the Eegent of France for $500,000. It is of a light blue color, 
and weighs 136 carats. The dotted line shows its form before cut- 



liant. The rose. The table. 523. How are the weight and value of diamonds 
estimated? 524. What does Fig. 194 represent? 195? What is its history? 



CARBON. 215 

ting. One of the largest diamonds is the Koh-i-noor (mountain of 
light), which came from India, and, according to native legends, 
was found 4.000 years ago. It has been in the hands of various 
families, and its possession has cost many murders and wars. It 
now belongs to the British crown. Fig. 195 represents the gem 
in its original shape and size. It was only surface-cut in the rose 
form. In 1852 it was cut into a brilliant weighing 162^ carats, 
after one third of it was removed. Fig. 146 represents its size and 
upper face. It took thirty-eight days to cut it, by steam, the 
operator working twelve hours a day without cessation. 

525. Graphite or Plumbago is another allot ropic form of 
carbon. It is found in beds in the earth, and crystallizes in six- 
sided plates of a metallic lustre, resembling lead; hence it is 
called Hack lead. Like the diamond, it resists the action of 
intense heat, and is useful to the chemist in making crucibles. It 
is friable, has an unctuous feel, and is used instead of oil, to 
relieve the friction of machinery. Being unaffected by the 
weather, it forms a valuable coating to protect iron- work from 
rust ; and, as it resists heat, it is fitted for stove polish. It is, 
however, often adulterated largely with lampblack, which may be 
detected by heating the suspected sample to redness, when the 
lampblack burns away. Its most important use is in the manufac- 
ture of pencils. The powder being subjected to enormous pres- 
sure coheres into blocks, and is then sawed into thin slices, and 
again into small bars, which are placed in grooved cedar sticks for 

Though apparently so soft, the particles of graphite are ex- 
tremely hard, and soon wear out the steel saws with which it is cut. 

526. Graphite, unlike diamond, may be artificially produced. 
When cast-iron, which has been melted in contact with an excess 
of carbon, i3 allowed to cool slowly, the carbon crystallizes out in 
the form of graphite. In the manufacture of coal gas, a layer of 
pure dense carbon, having a metallic lustre, is deposited upon the 
hottest parts of the retort. It is called gas caroon, and seems a 
modification of graphite, if, indeed, it be not itself an allotropic 
form of carbon. Beodie has produced a compound called graphic 
acid (C22H4O10), in which he considers the graphite as retaining 

lotropic state, and he hence terms it gro.jp~h.on, with the 
symbol Gr. 

525. What is graphite? Its properties and uses? 526. How is it artificially pro- 



216 INORGANIC CHEMISTRY. 

527. Charcoal is the third well-settled allotropic variety of 
carbon. When any organic substance, as wood, bones, sugar, is 
burned, with a partial exclusion of air, a black mass remains 
which is known as charcoal. It is ordinarily prepared by cover- 
ing large heaps of wood with tar, and burning them with a 
restricted supply of air, so as to prevent complete combustion, 
and only char the wood. The finer kinds of charcoal, such as are 
used for making gunpowder, are produced by distilling the wood 
in close iron retorts. 

528. Properties. — Charcoal is a black, brittle, inodorous, taste- 
less solid; a good conductor of electricity, but a bad conductor 
of heat, and perfectly insoluble in all liquids. It is oxidized by 
strong nitric acid, but resists the action of air and moisture, and 
is, therefore, very unchangeable. The timbers, and grains of 
wheat and rye, converted into charcoal 1800 years ago, at Hercu- 
laneum, remain as entire as if they had been charred but yester- 
day. Wooden posts are hence rendered more durable by charring 
their ends before placing them in the ground. The interior of 
tubs and casks are often charred for the same reason. 

529. The chief use of charcoal is as a fuel. When pure, it 
burns without flame, although it usually contains water which, 
during the combustion, is partially decomposed into carburetted 
hydrogen, and burns with a slight flame. A cubic foot of char- 
coal from soft wood, weighs from 8 to 9 lbs. ; from hard wood, 
from 12 to 13 lbs. ; hence, hard wood coal is best adapted to pro- 
duce a high heat in a small space. At high temperatures, charcoal 
has a very powerful affinity for oxygen ; therefore, it is of great 
value in reducing metals from their oxides, in the smelting furnace. 

530. Absorbent Powers of Charcoal. — Having the structure 
of the wood from which it was derived, charcoal is very porous, 
and possesses in a remarkable degree, the power of absorbing 
gases, and condensing them within its pores. It will absorb 90 
times its bulk of ammonia; 35 times its bulk of carbonic acid, 
and 9 times its bulk of oxygen. Freshly burned charcoal imbibes 
watery vapor from the air very greedily, and by a week's expo- 
sure, increases in weight from 10 to 20 per cent. Charcoal having 
the finest pores, possesses this power of absorption in the greatest 

duced ? 527. How is charcoal obtained ? 528. What are its properties ? Instances 
of its preserving action ? 529. How does it burn ? "What kind makes the best 
fuel ? How does it act in reducing metals ? 530. What makes it so absorbent ? 



CAEBON. 217 

degree ; the spongy sort least. ' A cubic inch of charcoal, ' says 
Liebig, 'must have, at the least computation, a surface of 100 
square feet.' 

531. The power of porous bodies to condense gases (72), in 
the case of carbon is of great importance. Charcoal absorbs 
noxious gases and offensive odors ; and 5 when crushed, foul water 
filtered through it, and tainted meat packed in it, are restored to 
sweetness. The charcoal from bones (bone black) is superior to 
wood charcoal for purifying purposes. It is extensively used in 
sugar refineries to decolorize syrups. Vinegars, wines, &c, are 
bleached in the same way. 

532. Charcoal not an Antiseptic.-— Charcoal is a powerful de- 
odorizer, and disinfectant, but it is not an antiseptic, or preventor 
of change, as has been supposed. In fact, it is an accelerator of 
decomposition. It was formerly thought that charcoal acted by 
simply sponging up the deleterious gases, and retaining them in its 
pores ; but it has been lately shown that, by means of its con- 
densing power, it is a powerful agent of destructive change. 
The condensed oxygen seizes upon the other gases present, and 
oxidizing them, forms new products. It thus changes ammonia to 
nitric acid, and sulphuretted hydrogen to sulphuric acid. The 
body of a dead animal packed in charcoal, emits no odor, but 
instead of being preserved, its decomposition is much hastened. 
This property has been made medically available in the form of 
charcoal poultice, to corrode away 

sloughing and gangrenous fiesh in ma- 
lignant wounds and sores. The dark, 
carbonaceous matter of soils is thus 
not only a magazine for storing gases, 
but a most potent agency of chemical 
change. 

533. Dr. Stenhouse, who in 1855 
first drew attention to the septic pow- 
ers of charcoal, has contrived ven- 
tilating arrangements in which the air 

of dwellings is filtered through it. He 

i • ? * ' i. ■ xi. m* ■ • Breath Filter. 

also invented a breath niter or respira- 

Give examples. How much surface has a cuhic inch ? 531. How is this property- 
utilized ? What kinds are best ? For what else is it used ? 532. What is its rela- 
tion to decay ? How is this proved ? Its use in medicine and in soils ? 533. What 
10 




218 



INORGANIC CHEMISTRY. 



tor consisting of a hollow case of wire gauze fitted to the face, as 
shown in Fig. 197. It is filled with coarsely powdered charcoal, 
which strains the air of its impurities before it enters the lungs. 

534. Lampblack is a modification of charcoal. It is the soot 
deposited from the burning of pitchy and tarry combustibles. The 
smoke is conducted through long horizontal flues terminating in 
chambers hung with sacking, upon which the lampblack is de- 
posited. It is used for making printers 1 ink and black paint. In 
combustibility it stands at the opposite extreme from the diamond, 
and so great is the surface it exposes to oxygen, that it has been 
known to take fire spontaneously in the open air. 

535. As in the diamond and graphite, the particles of the other 
varieties of carbon are extremely hard. Those of charcoal when 
rubbed between two plates of glass scratch it easily ; while pieces 
of anthracite coal have been used to cut glass like the diamond. 
The mineral coals found in the earth are forms of carbon, and will 
be noticed in Organic Chemistry. 



Fig. 198. 



§ VII. Compounds of Carbon and Oxygen. 

CARBONIC ACID. 

{Carbonic Anhydride, Fixed Air, MepTiitic Air, Choice Damp of 
Miners.) Sym. CO*. Equiv. 22. Sp. gr. 1,529. 

536. All the forms of carbon when burned in the air unite 
with oxygen and form carbonic acid. This is a colorless gas with 
a slightly sour taste and about half as heavy again 
as air. It exists abundantly in the mineral crust 
of the globe, in the fixed or solid state, and was 
hence at first called fixed air. It exists also in 
a free condition in the atmosphere, where it is 
indispensable to the vegetable kingdom. It 
was first described by Dr. Black in 1757, and 
is remarkable as the first gas discovered. 

537. Preparation. — Carbonic acid exists in 
limestone to the extent of 44 per cent, of its 
weight, and is most conveniently obtained by 
the action of an acid upon powdered marble, 

are Dr. Stenhouse's inventions? 534. What is lampblack ? How obtained? IU 
properties ? 535. What is said of the properties of carbon ? 536. What is carbonic 




Jar for making 
Carbonic Acid. 



COMPOUNDS OF CARBON AND OXYGEN. 219 

or chalk. Any strong acid will answer the purpose, but chloro- 
hydric is the best. The powdered mineral is placed in a jar and 
covered with water. A little^dilute acid is then poured down 
through the tube, Fig. 198 ; effervescence immediately takes place, 
and the gas escapes through the bent tube. It may be collected 
over water in the pneumatic trough, or, as it is heavier than the 
air, it will quickly displace it in an open vessel. The change is 
thus shown : 

CaO, C0 2 + HC1 = Cad, HO + C0 2 . 

A cubic inch of marble will yield four gallons of the gas. 

538. Test. — Carbonic acid combines with bases forming a class 
of salts known as the carbonates. Its test is solution of lime or 
clear lime water. When exposed to carbonic acid, it turns milky 
from the formation of insoluble carbonate of lime. Thus, if we 
expose a saucer of lime water to the air, in a short time its surface 
is covered with a thin film of carbonate of lime, proving that there 
is carbonic acid in the atmosphere. If we blow through a tube 
into a jar of lime water, it quickly becomes turbid from the same 
cause, thus showing that there is carbonic acid in the expired breath. 

539. It Extinguishes Fire.— To prove this, and to show also 
that it is heavier than air, we have but to place a lighted taper in 
a jar, and pour in carbonic acid from an- 
ther vessel, Fig. 199 ; the invisible current 
promptly puts out the light. It has been 
proposed to employ this gas on a large 
scale to extinguish fires. Some pulverized 
chalk and a bottle of acid are placed in 
a suitably constructed vessel, and when 
wanted for use, the bottle is crushed and 
the gas set free in large quantities. Such. 
is the construction of the ^ Fire Anni- 
Mator: This property of carbonic acid Pouring c^^Add. 
has been made available in extinguishing 

the accidental fires of coal mines. In one case an English mine 
had been on fire 30 years and burned a 9-foot seam of coal over 
an area of 26 acres, defying all efforts to quench it. Eight million 

acid? Why was it called fixed air? When and by whom was it discovered? 
537. How do we obtain it? What are the changes? 538. What are carbonates? 
"What is its test ? How do we prove its presence in the air ? How in the breath ? 
539. What is shown by Fig. 199? What is the fire annihilator? Where has this 




220 INORGANIC CHEMISTRY. 

cubic feet of the gas were poured into it for three weeks day and 
night, and the fire was thus completely extinguished. 

540. Poisoning by Carbonic Acid — When respired, carbonic 
acid is fatal to life. If pure, it produces spasm of the glottis, 
closes the air passages, and thus kills suddenly by suffocation. 
"When diluted with even ten times its bulk of air, and taken into 
the system, it acts as a narcotic poison, gradually producing 
stupor, insensibility, and death. This gas often accumulates at 
the bottom of wells, and in cellars, stilling those who may un- 
warily descend. To test its presence in such cases, it is common 
to lower a lighted candle into the suspected place, and if it is not 
extinguished, the air may be breathed safely for a short time. If 
the light goes out, it will be necessary before descending to let 
down dry-slaked lime, or pans of freshly burned charcoal to 
absorb the gas. 

541. Sources of Carbonic Acid.— It is produced throughout 
nature on an immense scale. Oxygen of the air seizing upon the 
carbon of the organic world, whether in rapid burning, or slow 
decay, gives rise to this gas. The combustion of a bushel of char- 
coal produces 2,500 gallons of C0 2 . It is produced by fermenta- 
tion, and the slow decomposition of organic bodies, and also by 
the respiration of the entire animal world. Each adult man 
exhales about 140 gallons per day. It is also produced by decom- 
positions and oxidations in the earth, and comes up with the 
waters which rise to the surface. It escapes in vast quantities 
from volcanoes, both active and extinct. Rising to the surface, 
often more rapidly than it is diffused into the air, it accumulates 
in invisible pools and ponds. Through the celebrated Grotto del 
Cane, in Italy, a man may walk unharmed, but a dog with its nos- 
trils near the earth, is suffocated on entering. The poison valley 
of Java is a lake of carbonic acid, filled with the bleached bones 
of dead animals. 

542. Effervescent Drinks. — The sparkling appearance and 
lively, pungent taste of various mineral waters are due to the car- 
bonic acid they contain. Water absorbs nearly its own volume 
of carbonic acid, but by means of a forcing-pump it may be made 
to receive a much larger proportion. ' Soda water ' is ordinarily 

property been successfully used ? 540. How does it act when breathed ? "What 
precautions should be taken? 541. What are the sources of carbonic acid? 
542 What is said of C0 2 in mineral waters? In soda water? In fermented 



COMPOUNDS OF CARBON AND HYDROGEN. 221 

only water charged with carbonic acid. Being overcharged, when 
the pressure is withdrawn, the gas escapes with violent effer- 
vescence. The effect is the same whether the carbonic acid is 
forced into the water from without, or generated in a tight vessel, 
as is the case with fermented liquors ; the gas gradually formed is 
dissolved by the water, and, escaping when the cork is with- 
drawn, produces the fuming and briskness of the liquor. 

543. Its Liquid and Solid Forms. — Under a pressure of 36 
atmospheres at 32°, carbonic acid shrinks into a colorless, limpid 
liquid lighter than water. When this pressure is removed, it 
does not suddenly resume its gaseous state, but evaporates with 
such rapidity, that one portion absorbs heat from another, and 
freezes it to a white solid, like dry snow. This solid carbonic acid 
wastes away but slowly, and may be handled, though if it rests 
long upon the ftesh, it disorganizes it like red-hot iron. 

544. Unlike other acids, the carbonic does not unite with 
water to form a definite hydrate. As a gas, a liquid, and a solid, 
it is anhydrous, and the later school of chemists designates it con- 
stantly as carhonic anhydride. 

545. Carbonic Oxide, CO, is a colorless, almost inodorous gas, 
which burns with a pale, blue flame. It is produced by burning 
carbon with an imperfect supply of air, and its formation may be 
observed in an open coal fire. At the lower part of the grate, 
where the air is abundant, carbonic acid is formed. As it ascends 
into the hot mass above, it loses half of its oxygen, becoming car- 
bonic oxide. The liberated oxygen combining with the carbon of 
the fuel, also produces an equal quantity of the gas. As the car- 
bonic oxide thus formed, rises to the surface of the fire, it burns 
to carbonic acid with a lambent, blue flame. This gas may be ob- 
tained pure and in great quantities by heating one part of prussiate 
of potash with ten of sulphuric acid, in a capacious retort. Car- 
bonic oxide when respired, is still more deadly than carbonic acid. 

§ VIII. Compounds of Carbon and Hydrogen. 

546. These form an extensive and important group, but they 
belong chiefly to Organic Chemistry ; two only will be here men- 
tioned. These substances have long been regarded as only of 

drinks ? 543. How is solid carbonic acid obtained ? 544. Why is it called carbonic 
anhydride ? 545. When is carbonic oxide formed ? Its properties when respired ? 



222 



INORGANIC CHEMISTRY. 



Fig. 200. 




Procuring Marsh Gas. 



organic origin, but Beethelot has lately succeeded in producing 
. them by the direct union of their elements. 

547. Light Carburetted Hydrogen, C 2 H 4 . — {Marsh Gas, Fire 
Damp.) This is a colorless, inodorous, tasteless, inflammable gas, 
which burns with a yellow, luminous flame. If diluted with air, 
it is not injurious to life. It may be produced by heating in a 

glass flask, a mixture of two parts of 
acetate of soda, three parts of caustic 
potash, and three of quicklime. It is 
called marsh gas, because it is a prod- 
uct of the decomposition of vegetal 
matter contained in the mud of stag- 
nant pools. It may be collected by 
inverting a jar and funnel in the water, 
and stirring the mud beneath, Fig. 200, 
when the gas rises into the jar in bub- 
bles. It is often disengaged in large 
quantities in coal mines : mixed with 
the air it becomes explosive, and con- 
stitutes the fatal fire damp. If the air is more than six times or 
less than fourteen times the bulk of the gas, the mixture explodes 
violently. Carbonic acid is produced by the combustion, so that 
those who are not killed by the burning or shock, are generally 
suffocated by the choke damp. 

548. In some places, this gas rises from the earth in such quan- 
tities, as to be utilized for purposes of illumination ; as in the 
village of Fredonia, 1ST. Y. In the deep wells sunk for brine and 
mineral oil, it often rises in such quantity as to be employed for 
driving the pumping engines, or for evaporating the liquids. 

549. defiant Gas, C 4 H 4 (Ethyline). — This gas may be pre- 
pared by mixing strong alcohol with five or six times its weight 
of sulphuric acid in a retort, and applying heat. It is colorless, 
tasteless, nearly as heavy as air, with a marked odor, very inflam- 
mable, and burns with a bright and intensely luminous flame. 
"When mixed with air, it is explosive, and derives its name (oil- 
former) from the circumstance of its forming an oily compound 
with chlorine. It was liquefied by Faeaday under great pressure. 



546. Are the hydro-carbons always of organic origin ? 547. What is light car- 
buretted hydrogen? How is it obtained? Why called marsh gas? What is 
fire damp? 548. Other natural sources? 549. What are the composition and 



COMPOUNDS OF CAEBON AND HYDROGEN. 



223 



Fig. 201. 



It is decomposed by electric sparks, depositing half its carbon, and 
forming light carburetted hydrogen. 

550. Illuminating Gas consists chiefly of the foregoing com- 
pounds of hydrogen and carbon. It is commonly produced from 
bituminous coal, by heating it in cast iron retorts, which are fixed 
in furnaces, and heated to redness by an external fire. Each re- 
tort receives a charge of 100 to 150 lbs. of coal every six hours, 
and in large gas works, several hundreds of them are kept at 
work day and night. At a moderate heat, tar and oil are pro- 
duced (957), but at a high temperature, gases are formed in large 
quantities. The principal products of this destructive distillation 
are a thick, black liquid, known as coal-tar, steam, various com- 
pounds of ammonia, sulphide of hydrogen, carbonic acid, light, 
carburetted hydrogen, olefiant gas, and a solid, friable, carbona- 
ceous mass known as coke. 

551. How Purified. — This heterogeneous mixture is wholly 
unfit for illuminating purposes till purified. The liquid and 
gaseous products, as 
they are set free, flow 
out from the retort, 
through a tube into a 
receiver, called the 
hydraulic main, in 
which the tar and am- 
moniacal liquor are to 
a great extent sepa- 
rated from the gaseous 
products. But being 
hot, they still retain 
various matters in a 
vaporous state, which 
would be deposited, 
and clog the gas pipes ; 
these are still farther 
separated by passing through the condenser, which consists of iron 
tubes surrounded by cold water. The gas is then passed through 
a mixture of lime and water (milk of lime), or through layers of 




The Gasometer. 



properties of olefiant gas? 550. "What is illuminating gas? How is it produced? 
What other products result? 551. How is the gas purified? Describe the gas- 



224 INORGANIC CHEMISTRY. 

damp slaked lime, which absorbs the carbonic acid and sulphide 
of hydrogen. It is then sometimes freely washed with water, 
which removes all its ammonia, when it is transmitted to a large 
storing vessel called the gasometer, Fig. 201. This is an immense 
sheet iron cylinder, open at bottom, and closed at top, which 
floats in a cistern of water. Two pipes open into the interior, 
one to deliver the purified gas which fills and raises the gasome- 
ter, and the other, which is connected with service pipes, to con- 
vey it away for consumption. The gasometer is balanced by 
weights which are so graduated as to compress the gas sufficiently 
to force it through the pipes to the farthest points desired. 

552. Composition. — This is variable, but it mainly consists of 
olefiant gas, light carburetted hydrogen, carbonic oxide, vapors 
of benzole and naphtha (958), with free nitrogen and hydrogen. 
Its value depends upon the proportion of olefiant gas, which is 
the chief light-producing compound. This is obtained first, and 
diminishes as the charge of coals is protracted, the poorer light- 
giving materials increasing. In one case, the gas first delivered 
contained 13 per cent, of olefiant gas, 82 of carburetted hydrogen, 
3.2 of carbonic oxide, and 1.3 of nitrogen. After 10 hours, it 
yielded 20 parts carburetted hydrogen, 10 parts of carbonic oxide, 
60 of hydrogen, and 10 of nitrogen. 

553. Gas from other Sources.— -Crude, refuse oil, which is 
unfit for burning, is sometimes converted into gas by being made 
to trickle into a retort, containing fragments of coke, or bricks 
heated to redness. It contains no sulphur products, needs no 
purification, and is rich in olefiant gas. Eesin, by being melted 
and treated in a similar way, yields a superior gas. An excellent 
gas is also produced from the distillation of wood ; but in point 
of economy, none of these sources can compete with coal. A 
pound of coal yields from three to four cubic feet of gas ; a pound 
of oil, 15 ; of tar, 12 ; and of resin, 10. 

554. Extent of its Use. — Illuminating gas has come into use 
entirely within the present century. It was first employed in Lon- 
don, in 1802, and its use has extended until nearly 500,000 tons of 
coal are consumed in a year by the establishments of that city alone, 

ometer. 552. Upon what does the value of the gas depend ? How do the propor- 
tions differ at different stages of the distillation? 553. What is said of gas from 
other substances? Its economy? 554. When and where was illuminating gas 
first employed ? How much is now consumed there ? What thought is suggested ? 



COMPOUNDS OF CARBON AND NITROGEN. 225 

producing 5,000,000,000 cubic feet of gas, and yielding an amount 
of light which would be equal to that given by ten thousand mil- 
lion tallow candles, six to the pound. How wonderful that sun- 
beams absorbed by vegetation in the primordial ages of the earth, 
and buried in its depths as vegetable fossils through immeasurable 
eras of time, until system upon system of slowly formed rocks have 
been piled above, should come forth at last, at the disenchanting 
touch of science, and turn the night of civilized man into day ! 

§ IX. Compounds of Carbon and Nitrogen. 

555. Cyanogen — Symbol, Cy. — Carbon and nitrogen do not 
unite directly ; but if animal matter, such as hides, horns, parings 
of hoofs, &c, be heated in a covered iron pot with carbonate of 
potash and iron filings, the carbon and nitrogen, as they are set 
free, combine to form a compound known as cyanogen, NC 2 . This 
substance was discovered by Gay Lttssac in 1814, and is remark- 
able as being the first chemical compound known to play the part 
of an element. Cyanogen proved to be an electro-positive body 
which would combine directly with the metals, like chlorine. It 
was, therefore, called a compound radicle, and represented by the 
symbol, Cy. The doctrine of compound radicles has been since ex- 
tensively carried out (910). "When produced as above, cyanogen 
unites with potassium and iron, producing the salt ferro-cyanide 
of potassium, K 2 FeCy 3 , HO, which forms the splen- 
did yellow crystals of commerce. The word Fig. 202. 
cyanogen signifies blue producer, as it is a con- 
stituent of the pigmeH^ prussian blue. 

556. Cyanogen is a transparent, colorless 
gas, poisonous if respired, and with a strong 
odor. It is very soluble in water, and hence 
must be collected in the pneumatic trough over 
mercury. It is reduced to a colorless, limpid 
liquid by a pressure of four atmospheres, and 
freezes into a transparent crystalline solid at 30°. 
It may be best procured in small quantities by 
heating a little cyanide of mercury in a test tube, 
Fig. 202. The salt is decomposed, the gas escapes, Burning Cyanogen. 

555. How may carbon and hydrogen be made to unite ? For what is cyanogen 
remarkable ? What doctrine has this led to ? Meaning of the word ? 556. What 
10* 




226 INORGANIC CHEMISTRY. 

and when ignited, burns with a beautiful blue flame edged with 
purple. Paracyanogen is an insoluble isomeride of cyanogen. 

557. Cyanohydric Acid, II Cy. {Hydrocyanic Acid, Prussia 
Acid.) — This is a colorless, transparent liquid, and so volatile that 
a drop on the end of a glass rod in the air solidifies by its own 
evaporation. It may be obtained by decomposing a salt of cyano- 
gen with strong acid, and then distilling it, the vapor having the 
odor of peach blossoms. It is one of the most insidious and deadly 
poisons, a few drops producing death in a few seconds. This acid 
is obtained by distillation of the kernels of bitter almonds and 
various fruits, and also from the leaves of the laurel, peach, &c. 

558. Cyanogen forms several compounds with oxygen, the 
best known of which are cyanic acid and fulminic acid. The lat- 
ter combines with metals, forming fulminates which are violently 
explosive. Hydrated cyanic acid is a volatile and highly corrosive 
fluid, which cannot be brought into contact with water without 
being instantly decomposed. Cyanuric acid is crystalline, soluble 
in water, and forms salts with metallic oxides. Cyamelide is a 
white, porcelain-like substance, absolutely insoluble in water. Yet 
these bodies are all isomeric, and may be converted into each other 
without loss or addition of constituents. 



CHAPTER YIIL . 

THE ATMOSPHERE. 

§ I. Its Physical Properties. 

559. This is the thin, gaseous medium which surrounds the 
globe. It is considered under a twofold aspect — in its mass, or as 
manifesting physical properties, and in its composition or chemical 
relations. The first belongs properly to Natural Philosophy, but 
it will be useful to recall a few points which are of constant appli- 

are the properties of cyanogen? How is it obtained ? 557. What is cyanohydric 
acid? How obtained? Its properties? Where is it found? 558. What com- 
pounds does cyanogen form with oxygen ? What are fulminates ? Properties of 
hydrated cyanic acid? Cyanuric acid? Cyamelide? What is said of these sub- 
stances ? 559. Under what aspects may the air be considered ? 560. What is the 



THE ATMOSPHERE — ITS CHEMICAL PROPERTIES. 



227 



Fig. 203. 




"Weighing Air. 



cation. "We have deferred the subject to this place, that the stu- 
dent may be familiar with the atmospheric constituents. 

560. Weight of Air.— It was first 
discovered about 200 years ago that 

. air, like all other forms of matter, has 
weight. If a light flask be exhausted, and 
then carefully counterpoised at the bal- 
ance, when the air is let in, it will be- 
come heavier and sink, Fig. 203. A 
/cubic foot of air weighs 538 grains, or 
something more than an ounce, and a 
room 40 feet square and 18 feet high 
contains about a ton. 

561. The Air Pump is an instrument 
for exhausting air from a tight vessel. 
In Fig. 204, P represents a piston which 
works air-tight in the cylinder c, and v v 
are valves of leather or silk which guard 
openings in the piston and the bottom of the cylinder. As the 
piston descends, v opens while ©' shuts. The tube t connects 
the pump with the receiver i?, which loses a portion of its air at 

each stroke. The receiver 
is a large glass vessel 
ground flat at the bottom 
so as to rest air-tight upon 
the pump plate. As its I' / 
| ^^ name implies, it receives 

objects for experiment. 

562. Elasticity.— If a 
small tight india rubber 
ball containing air be 

, , .,, . ,, Expansion of Air. 

placed withm the re- 
ump. ceiver and exhaustion take 

place, the air within will be dilated with force, and the ball will 
expand to several times its original size, as shown by the dotted 
line, Fig. 205. If the receiver be opened, the air rushes in, and 
the ball returns to its original dimensions. At first the air with- 
out and within the ball press against each other equally, but 



Fig, 204. 



Fig. 205. 





weight of the air? 561. Explain Fig. 204 What is the receiver ? 562. Describe 



228 



INOPwGANIC CHEMISTRY. 



Fig. 206. 




Fig. 207. 




when the outside pressure is withdrawn, the air within, by its 
inherent elasticity, expands into a larger bulk. Air exists in the 
pores of bodies, and by taking off the pressure, it 
expands and escapes. This is shown in Fig. 206, 
which represents an egg in a glass of water under 
an exhausted receiver. 

563. Atmospheric Pressure.— As the air has 
weight, it of course exerts pressure upon surround- 
ing objects. This pressure is in all directions, down- 
ward, sidewise, and upward. If a wine glass be 
filled with water, a card placed upon it, and then 

Esg m Receiver, inverted, the upward pressure of the air supports 
the liquid in the glass, Fig. 207. This pressure is 
considerable. If the hand be placed over the open 
end of a glass and the air be exhausted, it will be 
held as if with a powerful weight. The weight, or 
pressure of the air at the level of the sea, is 15 lbs. 
on every square inch ; this is, therefore, called an 
atmosphere : 30 lbs. would be two atmospheres, and 
1,500 lbs. a hundred atmospheres. 

564. The weight of the air is not the same at 
all times. Winds and storms keep it in motion, 

condensing and rarefying it, and thus affecting its pressure. There 
are also tides in it as in the ocean — great at- 
mospheric waves, which sweep over the earth, 
and with these movements, the pressure con- 
stantly varies. 

565. The Barometer.— Variations of pres^ 
sure are measured by the oarometer. To make 
this instrument, a glass tube is taken, 33 or 34 
inches long, closed at one end, and filled with 
quicksilver. It is then closed with the finger, 
as shown in Fig. 208, inverted, and its open end 
plunged into a vessel of quicksilver, o. The mer- 
cury then falls from Tc to w, leaving a vacuum, 
or place of no pressure in the upper end of the 
tube. The weight of the air pressing upon the 
mercury in the cup, supports the mercurial col- 
Barometer, umn 30 inches high. But as the atmospheric 

the experiment, Fig. 205. "What property of the air is here shown ? What is 



Upward Pres- 
sure of Air. 



Fig. 208. 




CHEMICAL CONSTITUENTS OF THE AIR. 



229 



Fio. 209. 



40 MILES 



pressure varies, the column rises and falls along the 
scale of some 2-J inches, attached to the tube. 

566. Pressure upon the Human Body. — Upon the 
body of a medium sized man, having a surface of 2,000 
square inches, the atmosphere exerts a crushing force 
of %),000 lbs., while the variation of an inch in the 
barometric column corresponds to a variation of 1,000 
lbs. pressure upon the body. That we are not con- 
scious of this pressure is, because the air within us 
presses outward with equal force. By ascending a 
mountain till the mercurial column fell to 14 inches, 
and by descending in a diving bell till it rose to 45 
inches, Humboldt exposed himself to a variation of 31 
inches, or 31,000 lbs. of pressure upon his person. 

667. Rarefaction in the Higher Regions. — As we 
rise from the surface of the earth, we have a portion 
of the atmosphere below us, and the weight of that 
above, of course, decreases. Elasticity then comes 
into play ; under less pressure the air expands, and as 
we ascend, it grows more and more rare, the barometer 
falling in exact proportion. Fig. 209 is designed to 
represent a vertical section of the atmosphere, extend- 
ing upward about 45 miles. The left hand column of 
numbers shows the height in miles above the sea level ; 
the right column the corresponding height of the ba- 
rometer in inches. A, indicates the height of the high- 
est peak of the Himalaya Mountains. The small cir- 
cle marks the greatest height reached by a balloon (six e 
miles), by Mr. Glaishee, in 1862 ; C, the sea level, 
and D, the deepest soundings yet obtained (by Capt. 
Denham, 8| miles). 

( 
§ II. Chemical Constituents of the Air. 

568. The atmosphere is a mixture of several gases ; 
nitrogen and oxygen constituting its bulk. There is a 
small proportion of carbonic acid and watery vapor, 
and variable traces of other substances. According to 
Dumas and Boussinoatjlt, its average composition by 

i • <«n *ti * ■* »«*% * - m . . -Atmospheric 

volume is 20.81 of oxygen, and 79.19 of nitrogen, in Column. 

shown by Fig. 206? 563. How is the pressure of the air shown ? How much is it ? 



230 INORGANIC CHEMISTRY. 

10,000 parts, or by weight 23.01 of oxygen, and 76.99 of nitrogen. 
This was ascertained by passing a stream of air slowly over a 
weighed quantity of heated copper in a tube. The oxygen was 
absorbed by the copper, the gain in weight of the tube indicating 
its quantity. The nitrogen was received into an exhausted flask, 
which was weighed before and after the experiment. The propor- 
tions of these two gases in the atmosphere are nearly invariable. 

669. If an artificial mixture of four parts nitrogen and one part 
oxygen be made, a candle will burn in it, and animals breathe in 
it as in ordinary air. The atmosphere is not a chemical com- 
pound, but a mechanical mixture ; its constituents being diffused 
throughout each other according to the great law of gaseous 
intermixture (74). 

570. The proportion of watery vapor in the atmosphere varie3 
with the temperature. It usually ranges from the ^ to the 2J0 °f 
the bulk of the air. By passing known quantities of air through 
carefully weighed tubes of caustic potash, the carbonic acid is 
absorbed, and its proportion determined. It varies from 3 to 6 
parts in 10,000 of air, and averages about one volume in 2,500. 
The quantity is variable within the limits above stated. It in- 
creases as we rise from the earth, and is less after a rain, which 
washes it down from the air ; it increases during the night, and 
diminishes after sunrise, is less over large bodies of water than 
over large tracts of land, and is more abundant in the air of 
towns, than in that of the country. Traces of nitric acid, ammo- 
nia, and carburetted hydrogen are also invariably present, and 
in the air of towns, sulphuretted hydrogen, and sulphurous 
acids. 

571. Proportions of the Atmospheric Elements. — A very clear 
idea of these quantities may be gained by supposing the air 
throughout to be of a uniform density, and its elements separated 
into strata, in the order of their specific gravities. In such a case 
the air would extend to the height of about five miles (Geaham). 

it? "What is this called ? What of its variability ? 565. What is the barometer? 
How is it made ? What causes the height of the column to vary ? 566. What is 
the pressure upon the body of a medium sized man ? To what variations did 
Humboldt expose himself? 56T. What is Fig. 209 designed to represent? 
568. What is the composition of the air? How was it ascertained? 569. What is 
the state of its elements ? 570. What is the proport : on of watery vapor ? How is 
the carbonic acid determined ? Where is it most abundant ? Of what other sub- 
stances are traces found? 571. How may we get a clear idea of these quantities? 



CHEMICAL CONSTITUENTS OF THE AIK. 



231 



Its greatest quantity of watery vapor, if condensed, would form a 
stratum of water about 5 inches deep ; the layer of carbonic acid 
would be about 13 feet deep; that of oxygen about 1 mile, and 
that of nitrogen about 4 miles in depth. 

572. Resulting Properties. — Each of the constituents of the 
air is essential to the present order of things. We have seen how 
imposing is the part played by oxygen, which is preeminently its 
active element. To duly restrain this activity, the oxygen is 
diluted and weakened by four times its bulk of the negative 
element, nitrogen. Their properties are thus perfectly adjusted to 
the requirements of the living world. Were the atmosphere 
wholly composed of nitrogen, life could never have been possible ; 
were it to consist wholly of oxygen, other conditions remaining 
as they are, the world would run through its career with fearful 
rapidity ; combustion once excited, would proceed with ungovern- 
able violence ; animals would live with hundred fold intensity, 
and perish in a few hours. 

573. Offices of Watery Vapor.— These are numerous and im- 
portant in a high degree. Three fourths of the weight of plants 
and animals consist of water, and they are continually absorbing 
and exhaling it ; while the rate of this vital operation depends 
upon the degree of moisture in the air. Were it perfectly dry, 
evaporation from leaves would proceed faster than supply from 
the roots, and the plant 
would quickly wither and 
die. A man weighing 154 
lbs. contains 116 lbs. of 
water. In absolutely dry 
air, he would quickly ex- 
hale this from skin and 
lungs, exhaust the tissues 
of their fluids, and shrivel 
to a mummy. 

574. Its Precipita- 
tion. — When two cur- 
rents of air of different 

temperatures, saturated with moisture, meet and mingle, the re- 
sulting mean temperature falls below the point necessary to hold 
all the water in a state of vapor, therefore a portion of it must 
572. If the proportion of oxygen were increased, what would follow ? 573. Were 



Fig. 210. 




Formation of Clouds. 



232 INORGANIC CHEMISTRY. 

fall. A gentle precipitation produces clouds, a more rapid one, 
rain. Thus, southerly winds loaded with humidity, coming in 
contact with the colder air of northern latitudes, usually give 
rain. For the same reason, the contact of air in motion with the 
cold surface of the earth, causes precipitation. This accounts for 
the fact that a larger amount of rain falls near the ground, than in 
the higher regions of the atmosphere. So currents of warm air 
striking against the side of a mountain are cooled, and, as they 
rise, produce the clouds and excess of rain which are peculiar 
to mountainous regions. In Fig. 210, the arrows show the 
course of the air currents, and the effect when they strike a 
mountain. 

575. When we remember that all the moisture which the 
atmosphere could hold, would make a sheet of water only 5 inches 
thick — no more, perhaps, than is annually deposited as dew, we 
can only be amazed at the vastness of the effects which it pro- 
duces in nature. So rapid and constant is the evaporation, that 
many times this quantity is precipitated in the course of a year. 
The amount of rain deposited is greatest at the equator, and di- 
minishes toward the poles. 

576. The Carbonic Acid which is poured into the atmosphere 
in prodigious quantities and from innumerable sources, is as 
necessary to the vegetable world, as is oxygen to the animal 
world. It is absorbed by the leaves, and minute as is its pro- 
portion, if it were withdrawn, the vegetable world would quickly 
perish. 

577. Liebig has shown that the air contains minute traces of 
ammonia, which are washed down, and may be detected in rain- 
water. Traces of nitric acid have also been frequently detected. 
This substance is thought to be formed by electricity, every flash 
of lightning which darts across the sky combining a portion of 
the oxygen and nitrogen along the line of its course, and forming 
this acid. The saline particles of the ocean-waves, as they are 
dashed into foam and spray, are carried by the winds far 
inland. All these substances are brought down by the rains, 
and aid to quicken the growth of vegetation. The odorous 

the air dry, what would follow? 574. What is the cause of clouds and rain? 
Why is there excess of rain near the ground, and on the mountain sides? 
575. What is said of the fall of rain ? 576. What is the office of carbonic acid in 
the air? 577. Whence come the ammonia and nitric acid of the atmosphere? 



PHLOGISTON. 233 

emanations of flowers, the miasms of marshes, and principles of 
contagion, though all producing effects upon the human body, 
cannot be collected from the air, and not nnfrequently elude the 
most delicate chemical tests. 

578. The Atmosphere and the Living World. — The relations of 
the atmosphere to living beings, the stability of its composition, 
and the wonderful forces that are displayed within it, have been 
but lately unfolded by science, and are full of surpassing interest. 
The vegetable world is derived from the air ; it consists of con- 
densed gases that have been reduced from the atmosphere to the 
solid form by solar agency. On the other hand, animals, which 
derive all the material of their structure from plants, destroy these 
substances while living, by respiration, and when dead, by putre- 
faction, thus returning them again in the gaseous form to the air 
from whence they came. In respect to air, the offices of plants 
and animals antagonize. "What the former derives from the air, 
the latter restores to it, thus maintaining its equilibrium and per- 
manence. "We shall return to this subject again in Physiological 
Chemistry. 



CHAPTEE IX. 

COMBUSTION AND ILLUMINATION. 

§ I. Historic Notice— Phlogiston. 

579. By the ancients fire was considered one of the four 
elements of nature— the most pure and perfect of them, which 
tended forever upward to its own place, the empyrean — the high- 
est heaven of pure fire and light. This doctrine held undisputed 
sway, so long as nature was not made a subject of experimental 
inquiry. But after a long period of laborious research on the part 
of the alchemists, a new order of facts was discovered, and a 
more definite theory of the cause and nature of fire was de- 
manded. Accordingly about the middle of the 17th century, the 
German chemist, Becchee, propounded a new hypothesis of com- 

Wliat other substances are mentioned ? 578. What is the relation of the atmo- 
sphere to living beings ? 579. What was the ancient theory concerning fire ? What 



234 INORGANIC CHEMISTRY. 

bustion, which was farther illustrated by his eminent countryman, 
Stahl, toward the close of the same century. This was the 
Phlogistic Hypothesis. 

580. How Combustion was Explained. — This doctrine as- 
sumed the existence of a rare ethereal principle called phlogiston, 
which could not be isolated, but existed in all bodies capable of 
burning. In the act of combustion phlogiston escaped, and the 
burning was caused by its escape. The products of combustion, 
which were deprived of phlogiston, and all bodies incapable of 
burning, were said to be dephlogisticated. When Peiestley bad 
discovered oxygen, which produced intense combustion, he be- 
lieved that it acted by powerfully attracting the phlogiston of 
combustible bodies, and hence named it dephlogisticated air. 

581. Difficulties of the Idea. — The fact that the metals when 
burned were changed to rust or cinders, was explained on the 
supposition that they consisted of this rust, or calyx as it was 
called, and phlogiston ; when they were burned, phlogiston 
escaped, and the cinders were left. But at length it was observed 
that the calyxes were heavier than the metals from which they 
were produced ; how then could they have lost anything ? The 
hypothesis, however, was sufficiently elastic to cover this objec- 
tion : it was replied that phlogiston was a principle of levity 
buoying up the substances with which it was associated, so that 
when it escaped, they became heavier. But the facts were no 
longer manageable by the hypothesis. 

582. Its Abandonment. — The discovery of oxygen, and the 
introduction of the balance (48), by Lavoisier, of France, gave 
the death blow to phlogiston. The general loosening of old 
ideas which marked the period o£ the French Kevolution, 
was eminently favorable to scientific changes, and an improved 
system of chemistry was introduced, which was the more cor- 
dially welcomed that it was clothed in the simple and rational 
attire of a new and admirable language. In accordance with the 
dramatic spirit of the times, at a festival, ' Madame Lavoisier, 
robed as a priestess, committed to the flames on an altar, 
while a solemn requiem was chanted, the phlogistic system of 
chemistry.' The new doctrine of the chemistry of oxygen was, 
therefore, at first known as the French system. The effect of the 

led to its overthrow ? 580. What was the phlogistic theory ? 581. How did it fail? 



COMBUSTION AND HEAT. 235 

new language was, in a great degree, to break connections with 
the past, and has, perhaps, led those who came after, to under- 
value the labors of the earlier chemists. 

583. Phlogiston served an important purpose in its day, and it 
scarcely becomes us to ridicule the doctrine, since we of the pres- 
ent, with our better light, are by no means exempt from the 
charge of entertaining ideas quite as absurd. Sir David Beewster 
remarks : c xVs to the generic idea of phlogiston, erroneous though 
it was and is, it is extant in science yet ; for it is impossible to see 
wherein caloric differs from it as a scientific conception, although 
elaborated with immensely greater precision, except that caloric 
is the matter of heat, while phlogiston is the matter of fire. Both 
phlogiston and caloric are substances wh^ph have no existence 
whatever in the external world ; they have both been convenient, 
though fictitious representatives of natural realities, and they have 
both been eminently useful in standing for certain phenomena in 
their several days, but the latter creation of the materializing 
tendency of unripe science, is not a whit better in essence than 
the former.' 

§ II. Combustion and Heat. 

584. Combustion a Chemical Process. — Combustion in its pop- 
ular sense, is that form of chemical action which is accompanied 
by the disengagement of heat and light, and which usually takes 
place between the oxygen of the air, and certain organic bodies, 
as wood, coal, oil, &c. The chemist, however, gives to the term 
a wider meaning, which includes all degrees of oxidation; the 
violent burning of iron in oxygen, or its slow rusting in the^air ; 
the rapid consumption of wood in the furnace, or its gradual 
decay ; the vital process of animal respiration, by which oxygen 
is changed to carbonic acid in the living body, and. warmth pro- 
duced, are all alike, to him, cases of combustion. 

585. It is an interesting circumstance that other cases of 
chemical action are brought about for the sake of the products 
formed, but in combustion the products are disregarded as worth- 



582. What led to its abandonment? "What is said of this change ? 5S3. To what 
is the theory of phlogiston compared ? 584. What is the common idea of combus- 
tion ? That of the chemist ? 585. How does it differ from other cases of chemical 



236 INORGANIC CHEM1STK1T. 

less, and the operation valued solely on account of the forces 
which are its incidental result* 

586- Bodies were formerly divided into combustibles and sup- 
porters of combustion. Atmospheric oxygen was held to be a 
supporter of combustion, while hydrogen, carbon, and iron, which 
burn in it, were called combustibles. But, if the conditions of 
the experiment Fig. 177' be reversed— that is, if a jet of oxygen 
be ignited in an atmosphere of hydrogen— precisely the same 
effect will take place ; oxygen will then be the combustible, and 
hydrogen the supporter of combustion. The fact is, the action is 
mutual, and of the same kind on the part of both elements ; the 
distinction is therefore groundless. 

587. The Process Self-supporting.— Every combustible sub- 
stance requires a certain elevation of temperature in order to 
ignite, and the maintenance of this temperature is essential to the 
continuance of the combustion. After a substance is once kindled, 
the heat given off by the rapid chemical action is usually more 
than sufficient to maintain the combustion until the burning body 
is consumed. 

588. Cause of the Heat. — It has been explained that chemical 
action produces heat by conversion of the motion of chemical 
atoms into heat vibrations. We have atoms separated and power- 
fully attracted, like lifted weights : they rush together, collision 
arrests motion, and their force is given out as heat. It is the clash 
or impact of the atoms of oxygen against the elements of burning 
bodies, which gives us the heat and light of combustion. By figur- 
ing to ourselves the atoms shot across the molecular spaces with 
intense force, and thus parting with their excess of motion, we 
have an explanation of the source of heat in combustion, which is 
in harmony with our latest knowledge of the nature of heat, and 
of its other modes of production, while in no other way is it pos- 
sible to explain its chemical origin. 

589. Upon what the Amount of Heat depends. — In all ordi- 
nary cases of combustion, the amount of heat set free depends 
upon the quantity of oxygen brought into action, rather than on 
that of the body burned. Hence, the combustible which unites 
with the most oxygen while burning, will give off the most heat. 

action? 586 What old distinction is said to be erroneous? 587. Why must 
combustion be first kindled? 588. What causes the heat and light of com- 
bustion ? Describe the conception. 589. Upon -what does the amount of heat 



COMBUSTION AND HEAT. 237 

Thus, hydrogen in burning, takes up weight for weight three 
times as much oxygen as carbon does ; consequently, it gives off 
three times as much heat. 

590. The complete burning of a combustible body requires 
the consumption of the same quantity of oxygen, whether the pro- 
cess goes on rapidly or slowly, and, in either case, the amount of 
heat set free is the same. Therefore, the intensity of the heat 
depends upon the rapidity of the combustion. Heat would be 
liberated from the burning of a pound of coal in ten minutes, six 
times as fast as if its combustion occupied an hour. This is the 
reason why the smith blows his fire, and why such powerful 
blowing apparatus is applied to blast furnaces ; they diminish the 
time of the combustion, and correspondingly increase its vehe- 
mence. The powerful blast or draft also serves to expel from the 
fire the products of combustion which would impede it if suffered 
to accumulate. Yet excess of air is detrimental to the burning 
process, by conveying away heat, thus cooling the fuel, and 
checking the rate of combustion. 

591. One pound of wood charcoal will raise from the freezing 
to the boiling point 73 lbs. of water ; 1 lb. of mineral coal will 
correspondingly heat 60 lbs. of water, and 1 lb. of dry wood will 
raise 35 lbs. of water through the same number of degrees. These 
are the highest results by careful experiments ; in practice we 
obtain a much lower effect, both on account of imperfect combus- 
tion, and from the fact that a large proportion of the heated air 
escapes through the chimney, before it has given off as great an 
amount of heat as it is capable of producing. The weight of air 
required to burn the fuel, is vastly greater than that of the fuel 
itself. It takes 11.45 lbs. of air to consume 1 lb. of charcoal, and 
as 1 lb. occupies nearly 13 cubic feet of space, the pound of char- 
coal will require about 150 cubic feet of air for its combustion. 

592. Kindling Temperature.— The temperature at which oxy- 
gen goes into rapid combustion, differs with different bodies. 
Thus phosphorus ignites at 150° ; sulphur at 480°, while the hy- 
drocarbons require a temperature of nearly 1000° to kindle them. 
The stability of the order of nature depends upon the gradation 

depend? Example. 590. Its intensity? How is this illustrated? How may 
excess of air be detrimental ? 591. Compare the heating effects of charcoal, min- 
eral coal, and wood. How much air is required to consume 1 lb. of charcoal ? 
592. How do kindling temperatures vary ? How has the art of kindling fires pro- 



238 INORGANIC CHEMISTRY. 

of the affinities between atmospheric oxygen, and the hydrogen 
and carbon of organic bodies. These are only brought into action 
at high temperatures. Did these bodies ignite at a much lower 
degree, like phosphorus, conflagrations, which are now compara- 
tively rare, would become universal. To 'make a fire,' requires 
an effort of reason, and, like the other arts, it has progressed with 
the advance of thought. First, the friction of pieces of wood ; 
then flints, steel, and tiuder ; and, lastly, with the progress of 
chemistry, phosphorized matches, the very perfection of con- 
venience. 

§ III. Flame and Illumination. 

593. Nature of Flame. — Flame is produced by the combustion 
of gases, and is, hence, fire in motion. Substances which burn 
with flame, are either gases already, or they contain a gas which 
is set free by the heat of combustion. But flame does not neces- 
sarily produce light. In the burning of pure oxygen and hydro- 
gen, there is intense flame, but so little light that it can hardly be 
seen. If, into this non-luminous flame, we sift a little charcoal 
dust, the particles of solid carbon are instantly heated to incan- 
descence, and there is a bright flash of light. The conditions of 
illumination are, therefore, first, an intense heat, and, second, a 
solid placed in the midst of it, which remains fixed, and gives out 
the light. 

594. The Compound Blowpipe.— These conditions are fulfilled 
most perfectly by means of the compound blowpipe of Dr. Hare. 

p IG 2ii. The two gases are collected in gaso- 

meters, or more conveniently in in- 
dia-rubber bags, Fig. 211, which 
are. connected by flexible tubes 
with the brass jet, Fig. 212 ; the 
flow being increased by pressure on 
the bags and controlled by stop- 
cocks. The gases are emitted to- 
Gas Bags for Blowpipe. gether and burned at the orifice, a. 

When ignited, they produce a blue flame which is hardly visible, 
but which has intense heating power, and produces the most 

gressed? 593. What is flame? What substances produce it in burning? What 
causes the light? What are the conditions of illumination? 594. Describe the 




FLAME AND ILLUMINATION. 



239 



Fig. 212. 




Blowpipe Jet. 



remarkable effects. Very fine wire twisted together, or a steel 
watch-spring, burns with a shower 
of scintillations. Substances which 
do not fuse in the hottest blast fur- 
naces melt in this heat like wax, or 
dissipate in vapor. 

595. The Lime Ball.— A little 
ball of lime, however, of the size of 
a pea, remains unaltered in the flame. 
It glows with a blinding brilliancy, 
producing what is known as the ' Drummond light,' the l Lime light,' 
or the ' Calcium light.' It is employed as a substitute for the ray3 
of the sun in the solar, or oxyhydrogen microscope, and is used in 
coast surveys for night signals. When reflected by a parabolic 
mirror in a pencil of parallel rays, it has been recognized in day- 
light at a distance of 103 miles. The hydrogen may be replaced 
without much disadvantage by ordinary coal gas. 

596. In all ordinary illuminations the principle is the same as 
that of the lime light. The substances employed are hydrocar- 
bons : the union of oxygen and hydrogen gives rise to heat, and 
the carbon particles at the same time set free in the heated space 
and made luminous, are the source of the light. 

597. How the Candle Burns. — The materials used for illu- 
mination, whether solids or liquids, are always converted into gas 
before burning. The candle first becomes a lamp, FlG 2 i3 
and then a gas burner. When lit, the heat radiates 
downward, so as to melt the material of the candle 
and form a hollow cup filled with the liquid com- 
bustible, Fig. 213, and thus the candle becomes an 
oil burner. From this reservoir, the wick draws 
up the oil into the flame. Here, in the midst of a 
high heat, and cut off from the air, it undergoes an- 
other change exactly as if it were enclosed and 
heated in a gasmaker's retort ; it is converted into 
gas, and in this form finally burned. As the wick 
rises into the flame, it -fills the interior as a sooty 
mass, and interferes with the combustion. To avoid 
this, wicks are sometimes plaited or twisted, so that Burning Candle. 

compound blowpipe. Its effects. 595 What is the Drummond light ? 596. What 
is the principle of ordinary illumination ? 597. Explain the process of burning a 




240 



INORGANIC CHEMISTRY. 



Fig. 214. 




The Flame Hollow. 



Fig. 215. 



in burning they bend over to the side of the flame, and are con- 
sumed. 

598. Structure of the Flame.— As the 
wick remains thus unconsumed in the in- 
terior of the flame, it is obvious there can be 
no fire there. If we lower a piece of glass 
or a wire gauze over a candle or gas flame, 
as in Fig. 214, we shall see an interior dark 
space surrounded by a ring of fire. This in- 
ner sphere is filled with dark unburned 
hydrocarbon vapors, which are enclosed by 
a shell of fire, or burning gas. If one end 
of a small glass tube be introduced into the 
candle flame, as in Fig. 215, these interior 
gases will be conveyed away, and may be 
lit at the other end. 

599. Order of the Combustion. — There 
is an order of combustion in the flame, which 
depends upon the order of affinities, and this 
is the hinging fact of illumination. In Fig. 
216, a represents the nucleus of hydrocar- 
bon vapor. If now oxygen from without 
had the same affinity for both its elements, 

they would be consumed together, with but little luminous effect. 

But the oxygen decomposes the gaseous compound, and, seizing 
upon the hydrogen first, surrounds a with the intensely 
heated space, ~b. At the same time the carbon particles 
are set free, and being heated white-hot, give out the mo- 
tion of light. The cone b is therefore the place of burn- 
ing hydrogen and the seat of illumination. The incan- 
descent carbon particles, as they pass outward, meet 
with oxygen at c, and are converted into carbonic acid 
in the outer cone. 

600. To prove the constant presence of free carbon 
in the flame, it is only necessary to introduce into it any 
cold body, as a knife blade, or *)iece of porcelain, when 

Shells of it will be copiously deposited upon it as soot. Fig. 217 
represents a cross section of the flame and the arrange- 




Gas from Flame. 




candle. 598. What do Figs. 214 and 215 represent ? 599. What Is tho ordor of 



FLAME AND ILLUMINATION. 



241 



Fi<*. 217. 




Cross Section of the 
Flame. 



ment of its parts ; CH the unburned carbon and hydrogen, H 
the sphere of burning hydrogen across which the carbon particles 
float, and lastly the sphere of burning carbon. 

60L By noting any common flame, it 
will be observed that it burns blue, and 
yields but little light at the base. This is 
because the oxygen at this point is so abun- 
dant as to burn simultaneously both hydro- 
gen and carbon. If we move a candle flame 
swiftly through the air, its light is dimin- 
ished for the same reason. The conical form 
of the flame is due to the currents of heated 
air ascending around it. 

602. The amount of light produced depends upon the inten- 
sity of the heat, as was before stated (399). Dr. Deaper found 
that a body at 2,600° emitted almost 40 times as much light as at 
1,900°. 

603. Effect of Cooling the Flame — If by any means the tem- 
perature of the flame falls below a certain limit it is immediately 
extinguished. The flame of a candle may be 
put out by lowering over it a coil of cold cop- 
per wire, Fig. 218. A piece of fine wire gauze 
held across the flame of a candle cools the 
combustible gases below the point of ignition, 
so that they rise through the meshes in the form of smoke, Fig. 
219. The gauze may even become red hot and still not allow the 



Fro. 218. 



Copper Coil. 



Fig. 219. 



flame to pass, so rapidly is the heat conducted 
away by the wire. Yet the cooled gases may 
be rekindled above, when the flame will go on 
burning as before, Fig. 220. 

604. Safety Lamp. — On this principle the 
safety lamp is constructed. The explosions 
of carburetted hydrogen gas in coal mines 
from the unprotected lamps of the miners, 
caused immense destruction of life, and vari- Gauze stops the Flame, 
ous arrangements had been fruitlessly contrived to prevent these 

combustion ? 600. How may the presence of free carbon in the flame be proved ? 
Explain Fig. 217, 601. Why is there little light at the base? To what is the 
conical form due ? 602. Upon what does the amount of light depend ? 603. Ex- 
plain Figs. 218 and 219. 604 What led to the invention of the safety lamp ? 
11 




242 



INORGANIC CHEMISTRY. 



Fig. 220. 




Gas burns above. 



Fig. 221. 



terrible accidents. At length Sir Humphry Davy took hold of 
the subject. He commenced a series of re- 
searches upon flame in August, 1815, and with 
such success as to produce the perfected lamp 
at the Koyal Institution of London in the suc- 
ceeding November. "With large liberality he 
presented it to the public, unrestricted by a 
patent : and it is interesting to remember that 
the researches on flame to which we are in- 
debted for the chief facts which have now 
been stated, were prompted by the noble de- 
sire of diminishing human suffering. As is frequently the case in 
all departments of investigation, so here ; others besides Davy con- 
trived safety lamps upon the same principle, unknown to each 
other. ** 

605. They consist simply of ordinary oil lamps enclosed in a 
cage of wire gauze which permits the light to pass out, but pre- 
vents all exit of flame, Fig. 221. The space within 
the gauze often becomes filled with flame, from the 
burning of the mixed gases which penetrate the net- 
work ; but the isolation is so complete that the explo- 
sive mixture without is not fired. Fatal explosions 
still occasionally take place, but they are due to care- 
lessness of the miners. An explosion occurred not 
long ago killing nearly a hundred people, and it was 
subsequently traced to the fact that a miner had broken 
a hole into the gauze of his lamp to hang it upon a 
nail! 

606. Influence of the Supply of Air. — As the in- 
tensity of light depends upon the rapid consumption 
of oxygen, there must be a free supply of air, and pro- 
vision for the ready escape of combustion products. 
The effect of a lack of air upon the flame may be seen 
Safety Lamp, by placing a glass cylinder over a burning candle so as 
to cut off the air ; the flame becomes dingy and feeble, Fig. 222. 
By slipping a couple of blocks under the cylinder, Fig. 223, the 
combustion becomes more energetic than it would be in the open at- 
mosphere, as by this means a rapid current of air is brought into con- 
Give its history. 605. Of what does it consist ? What is said of the effects of 
carelessness ? 606. What experiments illustrate the influence of supply of air ? 




FLAME AND ILLUMINATION. 



243 




Air cut off. 



Fig. 223. 




Air supplied. 



tact with the flame. If the cylinder be covered Fig. 222. 

at top, the flame is extinguished by the accumu- 
lation of the products of combustion. On the 
other hand too much air is injurious, as so large 
a proportion of oxygen mingles with the com- 
bustible gases that the carbon and hydrogen burn 
together. 

607. Argand Burner. — This is an arrange- 
ment for increasing both the supply of air and 
the burning surface of the flame. In the candle 
flame and gas jet, combustion only takes place on 
the outside. The Argand burner has a circular 
wick by which a second current of air is admit- 
ted to the interior of the flame, thus burning with 
a double surface. This effect is increased by a 
glass chimney contracted so as to deflect the as- 
cending outer current of air strongly upon the 
flame. See Fig. 224. 

608. Blowpipe Flame.— The high heat of the blowpipe flame 
is also due to the introduction of air into the centre of its flame. 

This is accomplished by blowing through a tube, 
the form of which and manner of using are seen in 
Fig. 226. On applying the blast the flame is de- 
flected to the horizontal position, as shown more 
clearly in Fig. 225, and it now presents two distinct 
portions which have opposite chemical offices ; a a 
represents the in- 
terior blue cone 
formed by the 
admixture of the 
oxygen with the 
unburned gases. 
The combustion 

is here complete 
Argand Burner. ^ ^ ^ Qf Blowpipe Flame. 

the flame most intense. From b to c is the luminous cone, which 
consists of unburned gases at a high temperature. These have a 



Fig. 224. 




Fig. 225. 




607. TVhat is an argand burner ? 608. How does the blowpipe illustrate the same 
thing? What is the reducing flame of the blowpipe? The oxidizing flame? 



244 



INORGAlSnC CHEMISTRY. 



Fig. 226. 



powerful tendency to combine with oxygen and take it from the 

oxides of metals; it therefore 
forms a reducing flame. At the 
extreme point of the flame there 
is a reverse effect. There, oxy- 
gen at a high temperature is 
mechanically carried forward, 
and if driven against a metal 
rapidly oxidizes it ; this point is 
therefore known as the oxidiz- 
ing flame. 

609. It is interesting to note 
that the elements which have 
been chosen to form combus- 
tible bodies universally are the 
only ones adapted to the pur- 
pose. Their products, carbonic 
acid and watery vapor, are transparent and therefore do not cloud 
and eclipse the flame. They are also inodorous, tasteless, and, 
in small proportion, innocuous ; while the oxides of all other com- 
bustible substances capable of existing in a gaseous state are 
pungent and irritating. 




Using the Blowpipe. 



CHAPTEE X. 

THE HALOGENS, OR SALT FORMERS. 

610- The bodies that compose this group are Chlorine, Bromine, 
Iodine, and Fluorine. They are characterized by their indifference 
to each other and their strong affinity for the metals, uniting with 
them to form a class of compounds of which chloride of sodium, 
or common salt is the type. Hence their name Halogens, or salt 
producers. 



609 What is said of the products of combustion? 610. What are the halogens? 
Why are they so named ? 611. When and by whom was chlorine discovered ? 
Where is it found ? 612. How is it obtained ? How is the reaction expressed ? 



CHLORINE AND ITS COMPOUNDS. 



245 



Fig. 227. 



§ I. Chlorine and its Compounds. 

CHLORINE. 

Sym. CI. Equiv. 35.5 Sp. Gr. 2.47. 

611. Chlorine was discovered by Scheele in 1774, while noting 
the action of chlorohydric acid upon peroxide of manganese. It 
is never found free in nature, but exists abundantly in the mineral 
world, chiefly in combination with the metal sodium, as common 
salt. Animals and vegetables also contain it in this condition. 

612. Preparation.— Soheele's method of obtaining chlorine by 
the action of chlorohydric acid on peroxide of manganese is still 
generally adopted. The manganese is placed 
in a flask provided with a safety tube for pour- 
ing in the acid, and a bent tube for conducting 
the gas to the receiver, Fig. 227. A little acid 
is first poured in and well shaken up with the 
manganese in order to wet every portion of it ; 
more acid is then added and a gentle heat ap- 
plied, when the gas is given off copiously. It 
may be collected over warm water or brine, 
and also by displacement, as seen in the figure. 
The greenish color of the gas from which it 
takes its name will indicate When the vessel 
is filled. The reaction may be thus expressed : 

MnO a ,+ 2HC1 = MnCl + 2HO + CI. 

Chlorine may also be prepared from common salt by the aid of 
sulphuric acid and oxide of manganese. 

613. Properties.— Chlorine is one of the most energetic of the 
elements, surpassing even oxygen under some circumstances. Or- 
dinarily it is a yellowish-green gas, but by a pressure equal to four 
atmospheres it may be condensed to a transparent, yellow liquid 
which remains unfrozen at — 220°. The gas has a peculiar, suffo- 
cating odor, and if inhaled, even when considerably diluted, pro- 
duces distressing irritation of the throat and lungs. When re- 
spired, however, in very minute quantities, it is not only harm- 




Making Chlorine. 



613. What are the properties of chlorine ? What does Fig. 228 illustrate ? 614. 



246 



INORGANIC CHEMISTRY. 



Fig. 228. 




Combustion in 
Chlorine. 



less, but is said to be beneficial to those affected with pulmonary 
disease. Chlorine maintains combustion; many 
bodies burn in it readily and some take fire in it spon- 
taneously, such as phosphorus, finely powdered 
antimony, and arsenic. Many organic compounds, 
rich in hydrogen, are decomposed by it so rapidly 
as often to burst into flame. A piece of paper 
saturated with oil of turpentine and plunged into 
a vessel filled with chlorine, Fig. 228, emits a dense, 
black smoke and usually ignites, from the rapid 
decomposition of the turpentine. Ohlorohydric 
acid is formed and carbon deposited. 

614. Cold water absorbs about two and a 
half times its own bulk of chlorine, the solution 
acquiring the color, taste, and smell of the gas. 
If this solution is cooled down to 36° F., a defi- 
nite crystalline hydrate of chlorine is formed, having the formula 
CI + 10 HO. Liquid chlorine may be readily obtained from these 
crystals by hermetically sealing them in a curved tube, Fig. 229, and 
applying a gentle heat. This liberates the chlo- 
rine, which, pressing upon itself, assumes the 
condition of a liquid. It may be distinguished 
from the water present by its yellow color. 
Chlorine solution readily dissolves gold, and 
also acts in some cases as a powerful oxidizing 
agent (608). Light decomposes chlorine wa- 
ter, giving rise to chlorohydric acid and free oxygen ; hence it is 
necessary that it be kept in bottles protected by some opaque 
covering. 

615. Bleaching Properties. — One of the most valuable quali- 
ties of chlorine is its bleaching power. A solution of it in water, 
or the moist gas, immediately discharges the colors of ordinary 
fabrics, indigo, common ink, &c. It is principally used in bleach- 
ing cotton cloth and rags of which paper is to be made. We 
have seen that oxygen is a powerful bleaching agent (457), and 
in chlorine bleaching it doubtless takes an important part. Not 
only does chlorine destroy the coloring matter by uniting with its 
hydrogen, but in moist bleaching it decomposes the water, setting 



Fig. 229. 




Condensing Chlorine. 



How are chlorine crystals obtained? Liquid chlorine? Properties of chlorine 



CHLORINE AND ITS COMPOUNDS. 247 

free oxygen which, in its nascent state, acts powerfully to oxidate 
and destroy the coloring particles. Dry chlorine will not bleach ; 
it acts only through the agency of water. But it is so powerful 
that, if the bleaching solution is not quickly removed, it corrodes 
and weakens the fabric. It has no action upon carbon, and there- 
fore does not bleach printer's ink. Nitrate of silver added to a 
solution containing chlorine, or a soluble chloride gives a white 
precipitate of chloride of silver, AgCl, which on exposure to light 
changes first to violet, and then to black. It is the universal test 
for chlorine. 

616. Allotropic Chlorine.— This element, like oxygen, has its 
active and passive condition. "When hydrogen and chlorine are 
produced and mingled in the dark, they do not unite ; if exposed 
to diffused daylight, they gradually combine, and if to direct 
sunlight, they combine explosively. Dr. Deaper found that 
chlorine gas which had been exposed to sunshine acquired the 
power of rapidly combining with hydrogen in the dark, and re- 
tained it for some time. When prepared in the dark, it is in a 
passive condition, but the effect of light so re-arranges its mole- 
cules as to exalt its activity and completely change its character. 
In its active state chlorine is highly electro-magnetic ; in its pas- 
sive state, it seems to become electro-positive, and capable of re- 
placing hydrogen in combination (922). The more refrangible 
rays are chiefly instrumental in producing this change. 

617. Compounds of Chlorine. — Owing to the active character 
of chlorine, it forms compounds with nearly all the elements. It 
unites directly with many of the metals, producing chlorides, and 
also forms several important combinations with the non-metallic 
elements. The metallic chlorides will be noticed under the met- 
als ; — we give here its more important non-metallic compounds. 

618. Chlorohydric Acid. HCl {Hydrochloric Acid, Muriatic 
Acid). — The conditions under which these elements unite have 
just been noticed: The result is chlorohydric acid, a transparent, 
colorless gas, endowed with intensely acid properties. Two vol- 
umes of hydrogen combine with two of chlorine to form four 
volumes of the gas, no condensation taking place. 



^vater? 615. How does chlorine act as a bleaching agent? 615. How does nitrate 
of silver act as a test for chlorine ? 617. What are the chlorides? 618. How is 
hydrochloric acid formed ? 619. What is Fig. 230 ? 620. What are the properties 



248 



INORGANIC CHEMISTRY. 



Fig. 230. 




619. Preparation. — For experimental purposes the gas may be 
readily obtained by beating a strong solution of cblorobydrio acid 
in a glass flask furnished with a perforated cork through which a 

bent tube passes for conducting the 
gas to the receiver. Fig. 230 is a con- 
venient arrangement for this purpose. 
The gas must be collected by dis- 
placement, as it is greedily absorbed 
by water. 

620. Properties. — Chlorohydric 
acid gas is unrespirable, very irri- 
tating to the eyes, and not a sup- 
^ porter of combustion.' It is some- 
what heavier than air, having a specific 
gravity of 1.24. Under a presure of 
40 atmospheres, it condenses into a 
colorless liquid which has never been frozen. "When allowed to 
escape into the air, the gas combines with its moisture so rapidly 
as to produce white fumes. So great is its affinity 
for water that a lump of ice placed in a jar of the 
gas is liquefied, and the gas instantly absorbed. 
Free chlorohydric acid forms with ammonia dense 
white clouds of sal-ammoniac, as may be shown 
by bringing near each other two glasses, Fig. 231, 
one containing the acid and the other the alkali. 

621. At a temperature of 40° F., water ab- 
sorbs about 480 times its bulk of chlorohydric 
^0^^^ acid gas, increasing in volume about one third, 
Gases producing a an d forming a colorless fuming, intensely acid 
liquid, having a specific gravity of about 1.247, 
known as muriatic acid, spirit of salt, &c. This solution is one 
of the most important requisites of the laboratory, and is also used 
for many purposes in the arts. The gas may be generated on a 
small scale by the action of dilute sulphuric acid on common salt 
aided by a gentle heat. Good proportions are two parts by weight 
of dilute acid to one part of salt. The gas is absorbed by cold 
water which is contained in a series of bottles connected with 
the generating flask, Fig. 232. The reaction consists in the de- 



Se.parating HC1. 



Fig. 231. 




of H, CI ? Explain Fig. 231. 621. What is muriatic acid ? Describe its preparation. 



CHLORINE AND ITS COMPOUNDS. 



249 



Fig. 232. 




Preparing solution of HC1. 



composition of the water of the sulphuric acid, its hydrogen 
taking the chlorine of the salt 
(which is composed of chlorine 
and sodium), and forming with 
it chlorohydric acid, while the 
oxygen unites with the sodium 
to form soda. The sulphuric 
acid combines with the soda, 
producing, if the acid is in ex- 
cess, a bisulphate, while the 
gas escapes, and is taken up by 
the water in the bottles. Ex- 
pressed in symbols we have 

NaCl + 2 HO, S0 3 = STaO, HO, 2S0 3 + HC1. 

622. The condensation of chlorohydric acid gas is attended 
with the liberation of a large amount of heat, which raises the 
temperature of the water, thus reducing its capacity for absorbing 
the gas. To obviate this, the bottles are surrounded by ice, or a 
mixture of ice and salt. In the manufacture of the acid on a 
large scale, the decompositions are carried on in iron cylinders. 
The acid is condensed in stoneware vessels arranged like Woulfe's 
bottles. 

623. Chlorohydric acid gas occurs in large quantities as an inci- 
dental product in the manufacture of carbonate of soda from com- 
mon salt. Until within a few years, the gas was allowed to escape 
into the atmosphere, where it condensed, and fell as a corrosive 
rain, to the great detriment of the surrounding vegetation. It is 
now condensed in large towers, built for the purpose, and con- 
nected with the furnace in which the salt cake or sulphate of soda 
is manufactured. Pure chlorohydric acid is colorless, but the 
commercial article has a yellow tinge due to organic impurities, 
free chlorine, iron, &c. 

624. Nitro-Chlorohydric Acid.— A mixture of chlorohydric 
acid with nitric acid, constitutes the aqua regia, or royal water of 
the alchemists, so named from the power it possesses of dissolving 
gold, the ' King of metals.' The mixture acts by setting chlorine 
free, which, at the moment of its liberation, attacks the metals, 



622. What precaution is necessary ? 623. Where is it now made in large quanti- 
11* 



250 INORGANIC CHEMISTRY. 

dissolving and combining with them. The proportions for the 
mixtures are two measures of chlorohydric to one of nitric acid. 

625. Chlorine and Oxygen.— The affinity of oxygen for chlo- 
rine is so feeble that the two elements can only be induced to 
unite by indirect means. The combinations are numerous, but we 
can only notice a few of the most interesting. 

626. Hypochlorous Acid, CIO, may be obtained by passing dry 
chlorine through a tube filled with red oxide of mercury. A 
portion of the chlorine takes the place of the oxygen, forming 
chloride of mercury, while another portion unites with the oxy- 
gen, at the moment of its liberation, forming hypochlorous acid. 
As a gas, its color is a shade darker than that of chlorine, and it 
has a similar pungent odor. It is a powerful oxidizing agent, and 
possesses remarkably strong bleaching power. 

627. Bleaching Compounds.— "When chlorine is passed through 
recently slaked lime (hydrate of lime), large quantities of the gas 
are absorbed, forming the bleaching powder of commerce. A few 
chemists regard this and the similar compounds of potash and 
soda, as formed by the direct combination of chlorine with the 
base, having the formula in the case of lime CaO, CI. The ma- 
jority, however, maintain that they are compounds of hypochlo- 
rous acid with the base, which would make the symbol of the lime 
compound CaO, CIO. According to this view, the substances 
formerly known as chlorides of lime, potash, soda, &c, are hypo- 
chlorites of these bases. 

628. Hypochlorite of Lime, CaO, CIO. — This is a white, spar- 
ingly soluble powder, used in great quantities for bleaching pur- 
poses. In the bleaching of cotton fabrics, the goods are first freed 
from all greasy impurities, and then digested in a solution of this 
powder. They are next dipped into very dilute sulphuric acid, 
where the chlorine is liberated, and exerts its bleaching power. 
This process requires to be repeated several times before the color 
is entirely discharged ; after which the goods are thoroughly 
washed in water, in order to remove all trace of acid from the 
fibre of the cloth. 

629. The change effected in modern days in the process of 
bleaching, is a striking example of the value of chemical skill as 

ties? 624. What is said of aquaregia? 625. Of the compounds of chlorine and 
oxygen ? 626. What is hypochlorous acid, and how is it obtained ? 627. What are 
the theories of the composition of bleaching compounds ? 628. How is the bleach- 



CHLOEINE AND ITS COMPOUNDS. 251 

applied to the industrial arts. Formerly, cotton and linen fabrics 
were bleached by steeping them in alkaline liquors, then boiling 
them in water, and exposing them for a long time upon the grass, 
where they were frequently sprinkled, and this was followed by 
soaking them for weeks in sour milk. This was repeated again 
and again, the process being not only slow and tedious, but 
requiring a large amount of manual labor, and a great extent of 
grass land. The substitution of dilute sulphuric acid for the sour 
milk, in dissolving out the alkaline matter, greatly reduced the 
time in this part of the process, while the subsequent application 
of chlorine still further shortened the operation, so that in two 
days is now accomplished what formerly took from four to eight 
months. 

630. Chlorine is a disinfectant. It acts in the same way as 
in bleaching, by decomposing noxious effluvia. The chlorides of 
lime, potash, and soda are the compounds best adapted to this 
purpose, as they gradually evolve the gas at ordinary tempera- 
tures. Chlorimetry is the name given to the process by which 
the percentage of chlorine is determined in those compounds from 
which it may be obtained as a bleaching agent. The most accu- 
rate method, as devised by Gav-Lussac, consists in ascertaining 
the amount of arsenious acid which could be peroxidized by a 
known weight of the bleaching powder. 

631. Chloric Acid, C10 5 . — This, the most interesting compound 
of chlorine and oxygen, has never been obtained in an unconi- 
bined form. It always retains one equivalent of water, ClOstEO. 
If chlorine gas is passed through a strong solution of caustic 
potash, it -is rapidly absorbed, and a bleaching liquid formed, 
which, on the application of heat, loses this property, and is con- 
verted into chloride of potassium and chlorate of potash. The 
chlorate of potash may be separated from the solution by crystal- 
lization, as it is less soluble than the chloride. Hydrofluo-silicic 
acid, added to a solution of these crystals, unites with the potash, 
carrying it down in an insoluble state, thus liberating the chloric 
acid, which may be obtained in a sirupy form, by evaporating the 
solution at a heat not exceeding 100°. A higher heat decom- 
poses the acid. While in this state, it is very unstable, being de- 

fcg effected? 629. How is the change in the mode of bleaching spoken of? 
630 Ilow docs chlorine act as a disinfectant ? What compounds are hest adapted 
for this, and why? What is chlorimetry? 631. How is chloric acid obtained? 



252 INORGANIC CHEMISTRY. 

composed by the presence of any combustible matter, and even 
by diffused daylight. 

632. Chlorates.— The chlorates are characterized by the ease 
with which they yield their oxygen on the application of heat, by 
their powerful affinity for combustible substances, and by scintil- 
lating when thrown upon ignited coal. They are used as a source 
of oxygen, and in the manufacture of fireworks. 

633. Chlorous Acid, Peroxide of Chlorine, and Perchloric 
Acid may be obtained by the decomposition of chloric acid. Sul- 
phuric acid, poured upon chlorate of potash, liberates chlorous 
acid in the form of yellow vapors, which are very explosive. 
Peroxide of chlorine is also explosive. It resembles chlorous acid 
in appearance, and dissolves in about twenty times its bulk of 
water, forming a powerful bleaching solution. Perchloric acid 
is the most stable of the oxides of chlorine, and readily forms salts 
with various bases, which are all soluble, and decomposable by 
heat. 

§ II. Bromine, Iodine, Fluorine. 

BROMINE. 

gym. Br. Equw. 80. Sjp. Gr. at 32°, 3.187. 

634. Bromine was discovered by Ballakd, a French chemist, 
in 1826, in the ' mother liquor,' or bittern, left after the extrac- 
tion of the crystallizible salts from sea water. This is the prin- 
cipal source of the element, although it is found in the waters of 
various saline springs, and in a few minerals. Bromine is pre- 
pared by introducing into the mother liquor a current of chlorine, 
which sets it free. Ether is then added, which, on agitation, 
takes up the bromine, and rises to the surface as a deep red 
stratum. 

635. Properties. — Bromine is the only element, except mercury, 
which exists as a liquid at ordinary temperatures. It is of a deep 
red color, and very volatile, with a disagreeable, irritating odor, 
from which its name is derived. It is a powerful poison, a drop 
on the beak of a bird producing instant death. It has bleaching 



632. Describe the chlorates. 633. What is said of chlorous acid? Peroxide of 
chlorine ? Perchloric acid ? 634. Where is bromine found ? How is it prepared ? 
635. Properties of bromine ? Uses ? 636. What are the sources of iodine ? Its 



BROMINE, IODINE, FLUORINE. 253 

properties, and is soluble in water. It is used in photography, 
and, in minute quantities, as a medicine. Like chlorine, it forms 
an acid with hydrogen, and also unites with oxygen, giving rise 
to bromic acid, the only known compound of these two elements. 

IODINE. 

Symb. L Equw. 126.8. Sp. Gr. 4.94. 

636. This useful substance was discovered by M. Cottrtois, 
of Paris, in 1811. He first observed it in kelp, or the ashes of 
sea-weed, and it is still obtained from this source for commercial 
purposes. It exists in mineral springs, and has also been found 
in minute quantity in certain minerals." In its preparation the 
ashes are leached, and the solution evaporated, until the more 
readily crytallizable salts are removed. The mother liquor, which 
contains the iodine as iodide of sodium, is then distilled with sul- 
phuric acid and oxide of manganese, when the iodine comes over 
as vapor, and is deposited in the form of brilliant, bluish-black 
scales, resembling plumbago in appearance. 

637. Properties. — Iodine is a non-conductor of electricity, and 
is sparingly soluble in water, though easily dissolved by ether or 
alcohol. When heated, it rises as a beautiful purple vapor ; hence 
its name, from iodes, violet-colored. In various forms, it is used 
extensively in medicine, but, taken in large doses, it acts as an irri- 
tant poison. The test for iodine is moistened starch, with which 
it forms a deep blue compound. If the iodine is in combination, 
it may be liberated by the addition of a little chlorine water, as it 
is necessary to the success of the test that it be in the free state. 
One part of iodine in a million of water may be detected .by this 
means. 

638. Iodohydric Acid, HI, may be obtained in the form of a gas 
by heating iodine in hydrogen. It is a strong acid with a pungent 
odor, very soluble in water, and readily decomposed by chlorine 
or bromine. Iodine combines with the metals, forming com- 
pounds remarkable for the beauty and variety of their colors. Its 
most important compound is formed by its union with potassium, 
which gives KI, or iodide of potassium. Like chlorine and 

preparation? 637. What are its properties? What its uses? "What is its test? 
638. What are the properties of iodohydric acid ? Other compounds of iodine ? 



254 INORGANIC CHEMISTRY. 

bromine, it unites with oxygen, but the compounds possess no 
general interest. 

FLUORINE. 

Sym. F. Equiv. 19. Sp. Or. 1.31. 

639. Fluorine is only known in combination. It exists in 
various minerals, but most abundantly in fluorspar (fluoride of 
calcium), from which it is obtained as fluohydric acid by means of 
sulphuric acid. It is also found in minute quantity in the bones 
of animals and the enamel of the teeth, to which structures it is 
supposed to give hardness. Fluorine forms compounds with all 
the metals, and with many of the non-metallic elements, but it 
cannot be induced to unite with oxygen. 

640. Fluohydric Acid, HF {Hydrofluoric Acid). — This may 
be obtained by decomposing fluorspar with sulphuric acid, the 
operation being usually aided, by a gentle heat. Owing to the 
powerfully corrosive quality of this acid, it is prepared in leaden 
vessels. If required perfectly pure, platinum or silver vessels are 
used. The acid, as thus obtained, is a fuming, white liquid, which 
requires the greatest care in dealing with it, as, if allowed to 
come in contact with the skin, it produces a deep and exceedingly 
painful sore, very difficult to heal. It combines with water with 
avidity, producing a hissing noise. Many of the metals dissolve 
in it, fluorides being formed, and hydrogen liberated. Potassium 
decomposes it with an explosion. 

641. The distinguishing characteristic of fluohydric acid is its 
corrosive action on glass. This may be shown by placing some 

powdered fluorspar, made into a paste with 

FlG - 233 - sulphuric acid, in a leaden cup, Fig. 233, and 

covering it with a plate of glass, previously 

smeared on one side with beeswax, through 

which characters have been traced with a 

fine-pointed instrument. The waxed side is 

placed next the mixture, and a gentle heat 

applied to the cup. After the lapse of half 

an hour, on removing the glass, and cleaning off the wax with the 

aid of a little oil of turpentine, the characters will be found eaten 

639. What is said of fluorine? 640. How is fluohydric acid prepared ? What are 
its properties ? 641. Explain the process of etching upon glass. 642. What is the 




SULPHUR AND ITS COMPOUNDS. 255 

into the glass. The acid has combined with the silica of the glass 
at the exposed points. This quality is taken advantage of to etch 
the labels on glass bottles that are to be used in laboratories and 
drug shops, where corrosive substances abound. 



CHAPTER XI. 

THE PYROGENS OR EIRE PRODUCERS. 

§ I Sulphur and its Compounds . 

642. The elements of this group, Sulphur, Selenium, Tellu- 
rium, and Phosphorus, are closely allied to each other and marked 
by their strong attraction for oxygen. 

SULPHUR. 

Sym. S. Equiv. 16. Sp. Or. 2. 

643. Sulphur is a brittle yellow, solid, highly inflammable, burn- 
ing with a bright blue flame, and is insoluble in water or alcohol, 
but soluble in bisulphide of carbon. It is a non-conductor of 
electricity, and but a poor conductor of heat. 

644. Sources. — Sulphur exists abundantly in nature, both free 
and in combination. It is found native in various volcanic 
districts, especially in the island of Sicily, where it is mined 
in immense quantity for the market. Many springs and small 
lakes, in which it is evolved in the combined gaseous state, often 
deposit it in considerable quantities. It exists in combination 
with various metals, forming sulphides, and, as a constituent of 
sulphuric acid, it is found in gypsum and other minerals. 

645. Sulphur exists in plants, entering their roots in some 
soluble combination, and is present in a free state in the bodies of 
animals, chiefly in their muscular parts. It exists in eggs, and 
discolors the silver spoons with which they are eaten by forming 
the black sulphide of silver. The efficiency of many preparations 
for staining the hair black depends upon the lead they contain, 
which unites with the sulphur of the hair. 

distinctive property of this group? 643. What are the properties of sulphur? 
644. What are its sources ? 645. Where else does it exist ? 646. How is it purified ? 



256 



INORGANIC CHEMISTRY. 



Tig. 234. 



646. Sulphur is volatile, and sublimes by beat. Advantage is 
taken of this property to separate it from the mineral impurities 
with which it is found associated. It undergoes a rough distilla- 
tion in earthen retorts. Iron pyrites contains 50 per cent, of sul- 
phur, which is separated either by roasting it in large heaps in 
the air, and collecting the melted sulphur in cavities, or by heat- 
ing the pyrites in tubes, and running off the sulphur into vessels 
of water. 

647. Its Forms. — In commerce, sulphur exists in forms due to 
the different modes of its preparation : 1st, as flour of sulphur, a 
pale, yellow, gritty powder, obtained by sublimation ; 2d, as milk 
of sulphur, where it is procured in a very minute state of subdi- 
vision, by dissolving sulphur in a solution of an alkali, and pre- 
cipitating it with an acid ; 3d, roll sulphur, or brimstone, obtained 
by running it into moulds in the melted state. 

648. Its Allotropic States.— -These are three. First, crystals 
which take the form of right, rhombic octa- 
hedrons, Fig. 234. They occur in nature, and 
may be produced by evaporating a solution of 
sulphur in bisulphide of carbon. These crys- 
tals have a sp. gr. of 2.05, and undergo no 
change in the air. The second form is that of 
oblique, prismatic crystals, which may be ob- 
tained by melting ordinary sulphur in a cruci- 
ble, v and after it has cooled breaking the ves- 
sel, when the still fluid portion flows out, leaving a mass of crys- 
tals attached to the inner surface of the crucible, Fig. 235. These 

have a sp. gr. of 1.98, are not permanent in 
the air, and require a higher temperature to 
melt them than the former. 

649. The third allotropic condition is ob- 
tained by the action of heat. Sulphur melts at 
239° into a thin, pale, yellow liquid, in which 
solid sulphur sinks. If the heat is raised to 
480°, it changes into a thick, tenacious, mo- 
lasses, colored body, which, if poured into cold 
water, becomes soft and elastic, like India rubber. In this state it 




Sulphur Crystals 



Fig. 235. 




Crystals by Fusion. 



How obtained from pyrites ? 647. What is flour of sulphur ? "What is milk of sul- 
phur? What is roll sulphur? 648. What is the first allotropic form of sulphur? 




SULPHUR AND ITS COMPOUNDS. 257 

is used to take impressions of medals, coins, &c. ; but it gradually 
resumes its former brittle condition. Sulphur is consumed largely 
in the manufacture of gunpowder, friction matches, sulphuric acid, 
and in medicine. It has an extensive range of affinity, ranking 
next to oxygen in this respect, and forming many important com- 
pounds. 

650. Sulphurous Acid, S0 2 .— When sulphur is ignited in the 
air, or in pure oxygen, Fig. 236, it burns with a Fi& m 
beautiful blue flame, and forms sulphurous acid. 
This is a transparent, colorless gas, having a pun- 
gent suffocating odor familiarly known in the 
case of a burning match. It extinguishes com- 
bustion ; hence sulphur is often thrown into the 
fire to quench the burning soot of chimneys. It 
has a strong attraction for water. Allowed to 
escape into the air, it forms white fumes with its 
moisture, and a piece of ice thrust into the gas is Making^phurous 
instantly liquefied. Water at 60° takes up large 

quantities of this acid, the solution formed having the taste and 
smell of the gas. By cold or pressure it condenses into a liquid, 
and evaporates so fast that the cold generated will freeze water 
even in a red-hot crucible. 

651. Sulphurous acid is used as a disinfectant, and in bleach- 
ing woollen and straw fabrics. The goods are moistened, and 
suspended in large chambers, or, in a small way, they are put in 
inverted barrels, and exposed to the fumes of burning sulphur. 
The effect is produced, not by destroying the coloring matter, as 
in the case of chlorine, but by' the, union of the acid with the col- 
oring matter, which forms a white compound. If a red rose is 
held over burning sulphur, it is whitened, but the color is at once 
restored by weak sulphuric acid, which, being stronger, discharges 
sulphurous acid from combination. If woollens, after sulphur 
bleaching, are washed with a strong alkaline soap, the acid is neu- 
tralized by the alkali, the coloring matter liberated, and the yel- 
lowish color restored. 

652. Sulphurous acid may be conveniently prepared by heat- 
ing strong sulphuric acid with copper turnings. One equivalent 
of the acid parts with one equivalent of its oxygen, thus liberat- 

The second ? 649. The third ? For what is it used ? 650. How is sulphurous acid 
formed ? What are its properties ? 651. For what is it used ? How does it act in 



258 



INORGANIC CHEMISTRY. 



ing the sulphurous acid gas, while the oxide formed unites with 
another proportion of the acid, producing sulphate of copper. 

653. Sulphuric Acid, So 3 HO. — This powerful acid is of great 
interest to chemists and manufacturers. It is found native in the 
craters of manv volcanoes, and in the water of mineral springs. 
It was formerly prepared by distilling dry sulphate of iron (green 
vitriol) ; hence its old name, oil of vitriol. Now, however, it is 
usually obtained by combining one equivalent of oxygen with 
sulphurous acid. S0 2 is thus converted into S0 3 . 

654. Sulphuric acid may be prepared on a small scale by an 

Fig. 237. 




Fig 238. 



Arrangement for Preparing Sulphuric Acid. 

apparatus represented by Fig. 237. A large glass balloon, a, is 
connected by tubes with three flasks. Flask b supplies it with 
sulphurous acid ; c, with deutoxide of nitrogen ; d, with steam, 

and \he short tube 
furnishes air. These 
four substances react 
upon each other with 
the continued pro- 
duction of sulphuric 
acid. In the manu- 




Manufacturing iSulpkuric Acid. 



factory the balloon is represented by large chambers lined with 
sheet lead, and the flasks by furnaces, Fig. 238. In one furnace 
sulphur is heated, and pours into the chamber sulphurous acid, 
S0 2 . In another, nitre is heated in an iron pot with sulphuric acid, 

bleaching? What restores the color? 652. How may S0 2 "be prepared? 653. 
What is sulphuric acid ? What gave it its old name? 654. Describe the process 



SULPHUR AND ITS COMPOUNDS. 259 

by which fumes of nitre acid, N0 5 , are produced and delivered 
into the chamber. The N0 5 is quickly deprived of an atom of oxy- 
gen by the sulphur, and becomes N0 4 . Steam and air are thrown 
into the chamber by another flue, and thus the conditions of action 
are secured. 

655. The process depends upon the property possessed by the 
higher oxides of nitrogen of oxidizing sulphurous acid at the ex- 
pense of the oxygen of the atmosphere. The sulphurous acid is 
converted into the sulphuric, the oxygen being derived from the 
air, and the deutoxide of nitrogen being the carrier that transports 
it. A small quantity of 1TO 2 may thus form an endless quantity 
of S0 3 . These changes are represented in the following scheme. 



! FROM AIR, 20 






20 


1 \ 
I FROM THE \^ 

1 FURNACE, N02 =- N O4 

1 AS STEAM, HO \ 






H0 \ \ 






FROM THE ^v. \ 

j FURNACE, S02*^/ S N^ 

1 - - 


2(SO a 


HO) 


^^^ 2(S0 3 HO) 



656. The large chambers of the manufactory are divided by 
leaden partitions with narrow openings, which serve to facilitate 
the intermixture of the gases as they pass on through the apart- 
ments. The bottom of the chamber is always kept covered with 
water to the depth of two or three inches, to absorb the acid as 
it falls. When the water has acquired a density of 1.5, by the 
absorption of acid, it is drawn off and boiled down in glass or 
platinum retorts, until it has a specific gravity of about 1.8. The 
acid thus obtained contains one equivalent of water to one of acid, 
SO3HO, and constitutes the ordinary sulphuric acid of commerce^ 

657. Properties.— Sulphuric acid has a thick, oily appearance, 
is without odor, and has at first a soapy feel, but it speedily cor- 
rodes the skin, causing an intense burning sensation. It is the 
most powerful of acids, and has an intense affinity for water. 
TVhen a splinter of wood is dipped into it for a short time, it turns 
black, the acid taking away from it the elements of water, and 
leaving the carbon. In like manner, it decomposes and chars the 

of its preparation ? 655 Upon what does the action depend ? How is it effected ? 
656. What further occurs in the manufactory? 657. What are the properties of 
sulphuric acid. What is said of its affinity for moisture? What effects accom- 




260 INORGANIC CHEMISTRY. 

skin and most other organic substances by removing their water. 
If a little concentrated acid is exposed to the open air in a shallow 
& nnn dish it will soon double its weight from the moisture 

Fig. 239. ° 

absorbed. When sulphuric acid and water are mixed 

they shrink in bulk, and heat is produced. A mixture 

of four parts concentrated acid to one part water, Fig. 

239, evolves sufficient heat to boil the ether in a test 

tube. The concentrated acid freezes at about —30°, and 

Bcmng D0 ^ s at 640°. Pure sulphuric acid is colorless, but slight 

Ether, traces of organic matter, as dust or straws, turn it of the 

dark shade usually seen in commerce. The commercial acid is 

cheap, but impure, containing traces of lead, arsenic, potash, and 

chlorohydric and sulphurous acids. 

658. Sulphuric acid is extensively used in the manufacture of 
carbonate of soda and chlorine, of citric, tartaric, acetic, nitric, 
and hydrochloric acids, of sulphate of soda, sulphate of magnesia, 
and various paints, also in dyeing, calico printing, gold and silver 
refining, and in purifying oil and tallow. Its chemical uses are 
innumerable. The test for sulphuric acid is chloride of barium, 
with which it forms a white insoluble salt. 

659. Nordhausen Sulphuric Acid.— This is manufactured by 
the original process — the distillation of dried sulphate of iron in 
earthen retorts. It is a dihydrate, having one equivalent of water 
to two of acid, 2S0 3 + HO, and is the strongest variety of sul- 
phuric acid. It derives its name from being manufactured in the 
town of Nordhausen, in Saxony. 

660. Sulphuric Anhydride, S0 3 .— -This maybe obtained in the 
form of a white snowy solid, by distilling the Nordhausen acid, 
and collecting the fumes which pass over in a receiver surrounded 
by a freezing mixture. While in this condition, it exhibits no 
acid properties, and may be handled with impunity, if the hands 
are dry. But it fumes in the air, and rapidly absorbs moisture. 
"When thrown into water it hisses like a hot iron, and the solu- 
tion thus formed possesses all the properties of the ordinary acid. 

661. Hydrosulphuric Acid, HS {Sulpltydric Acid, Sulphuretted 
Hydrogen, Sulphide of Hydrogen). — This is a colorless, transparent 
gas, having the well-known odor of decayed eggs. It is feebly 

pany their union ? What is said of the commercial acid ? 658. For what is it 
used ? What is its test ? 659. What is the Nordhausen acid ? 660. How is the 
anhydride obtained ? What are its properties ? 661. Give the composition of 6ul- 



SULPHUR AND ITS COMPOUNDS. 



261 



acid, and burns with a pale blue flame, producing sulphurous acid 
and water. When breathed it is highly poisonous, and even when 
much diluted with air it has been proved fatal to many of the 
lower animals. By pressure the gas may be condensed to a color- 
less, limpid liquid, which freezes at —122°, the frozen portion sink- 
ing in the liquid. It readily dissolves in water, imparting to the 
solution its own taste and smell, as well as its slightly acid prop- 
erties. This gas is an abundant natural product from sulphur 
springs and the decay of organic matter containing sulphur, as 
albumen of eggs, flesh, &c. 

662. Preparation. — It is usually obtained by decomposing pro- 
tosulphide of iron with dilute sulphuric acid, 

FeS + S0 3 , HO = FeO, S0 3 + HS. 



Fig. 240. 



Fig. 240 represents a convenient ar- 
rangement for its evolution. The sul- 
phide of iron should be broken into 
small lumps and placed in the flask. The 
cork and tubes may then be adjusted, 
and first water and then sulphuric acid 
poured in through the funnel tube. The 
gas is absorbed by the water of the sec- 
ond vessel. The solution must be kept 
in tightly secured bottles, as, if exposed 
to the air, it is gradually decomposed. 
Hydrosulphuric acid is one of the most 
important chemical reagents, and is used Preparing Sulphuretted Hydro- 
for precipitation of the metals. 

663. Bisulphide of Carbon, CS 2 (Sp. Gr. of Liquid, 1.272 ; of 
Vapor, 2.644). — This is a very volatile, colorless liquid, boiling at 
118.5°, has a sulpurous odor and pungent taste. It has never been 
frozen, and is used in thermometers which are to measure very 
intense degrees of cold. It is highly inflammable, burning with a 
blue flame, and yielding carbonic and sulphuric acids. It dissolves 
sulphur, phosphorus, and iodine, and is dissolved in ether, but not 
in water. It is produced by bringing vapor of sulphur into con- 
tact with red-hot charcoal, the compound vapor being condensed 




phuretted hydrogen. What are its properties? 662. How is it prepared? Ex- 
plain Fig. 240. For what is it used ? 663. What is bisulphide of carbon ? State 



262 LNORGANIC CHEMISTRY. 

in cold vessels. From its high dispersive power over light, it is 
used to fill hollow prisms of glass for spectroscopic observations. 

§• II. Selenium and Tellurium. 

SELENIUM. 

Sym. Se. Equiv. 39.7. Sp. Gr. 4.8. 

664. This is an element of rare occurrence. It has not been 
found free, but usually occurs in combination with iron, copper, 
or silver. It is a brown, brittle solid, of metallic lustre and a 
glassy fracture. It presents a strong resemblance to sulphur, 
uniting with oxygen to form acids corresponding to the sul- 
phurous and sulphuric, and with hydrogen to form the selenide 
of hydrogen, a compound, if possible, more offensive than sulphide 
of hydrogen. 

TELLURIUM. 

Sym. Te. Equiv. 64.5. Sp. Gr. 6.6. 

665. A rare substance, found sometimes native, but generally 
combined with metals. It has a metallic aspect resembling bis- 
muth, and was formerlly classed with the meta]s, but it is now 
placed with sulphur and selenium on account of its strong anal- 
ogy with these bodies. Its compounds with oxygen and hydro- 
gen resemble those of its associates. 

§ III. Phosphorus and its Compounds. 

PHOSPHORUS. 

Sym. P. Equiv. 31. Sp. Gr. 1.83. 

666. This interesting body is a soft, colorless, half-transparent, 
waxy solid, so extremely inflammable that it takes fire in the open 
air by the heat of the slightest friction, and burns with great 
violence, emitting a brilliant flame, and dense, white fumes of phos- 
phoric acid. If quietly exposed to the air it undergoes slow oxi- 
dation, emitting white vapors of an odor like garlic. It must be 

it properties. Uses. 664. What is selenium ? 665. What is tellurium ? 666. What 
are the properties of phosphorus ? Why is it kept under water ? What are its 



PHOSPHORUS AND ITS COMPOUNDS. 263 

handled with caution, as the burns it produces are deep and diffi- 
cult to heal. From its inflammability it is kept under water. It 
is insoluble in water; partially soluble in ether, but dissolves 
readily in bisulphide of carbon and various oils. 

667. Source and Preparation. — Phosphorus combines with 
oxygen, forming phosphoric acid, and then unites with lime, produ- 
cing phosphate of lime. In this form phosphorus exists in bones, 
the phosphate of lime forming the mineral portion. The skeleton 
of a man contains from 1J to 2 lbs. of phosphorus/ To obtain it, 
the bones are first burned, and, the organic matter being con- 
sumed, they are reduced to powder and soaked in concentrated 
sulphuric acid. This decomposes the phosphate, removing two 
thirds of the lime. The remainder is then heated to a high tem- 
perature with charcoal in a close vessel. The carbon unites with 
the oxygen, liberating the phosphorus, which rises in vapor, and 
is condensed in water in the shape of yellow drops. These are 
melted under water and forced into tubes, thus forming the ordi- 
nary stick phosphorus. 

668. Discovery. — Phosphorus was discovered by Brandt in 
1669. The name signifies hearer of light, and was given on ac- 
count of its property of being luminous in the dark. In all 
its characteristics, it was a very extraordinary body. c If 
touched it took fire and burned furiously, exhaling a dense white 
cloud, which gathered like fleeces of snow, but, unlike snow, hiss- 
ing like a red-hot iron when touched with water or, if brought 
into contact with the body, blistering it like living fire.' "We may 
imagine the mingled wonder and dread of the devout alchemists as 
they passed precious little bits of it around among the initiated 
under a name which hinted their dark suspicions — ; the Son of 
Satan.' 

669. Phosphorescence. — If solutions of phosphorus in ether 
be spread upon the face in the dark, it causes a pallid glow, which 
soon passes away. The cause of this self-shining of phosphorus is 
probably its slow oxidation. Berzelitjs stated that it became 
luminous in nitrogen, hydrogen, or even in a vacuum, but 
Schrotter's more careful experiments show that to produce the 
effect a little oxygen must always be present. 

670. Its Allotropic Forms. — Among the marked properties 

eolvents ? 667. What is its source ? How is it obtained ? 668. How was it at first 
regarded? 669. How may phosphorescence he exhibited? To what is it due? 



264 INORGANIC CHEMISTRY. 

of this singular substance is the diversity of its allotropic con- 
ditions. It assumes six different forms. The first is the common 
transparent state, or vitreous phosphorus. When this is exposed 
to light under water it changes to the second variety, which is 
white, opaque, and less fusible. The third is a symmetrical 
crystal of the regular system, formed by evaporating some of its 
solutions. The fourth is a black, opaque variety, produced by sud- 
den cooling of the melted phosphorus ; fifth, a soft elastic sub- 
stance analogous to viscous sulphur, and formed by suddenly 
cooling phosphorus when near its boiling point ; and, sixth, a red 
amorphous sort, which may be obtained by exposing vitreous phos- 
phorus to the rays of the sun between two plates of glass. 

671. This red amorphous variety may also be produced by heat- 
ing common phosphorus in an atmosphere of carbonic acid, when 
it is obtained as a brick-red powder. As vitreous phosphorus may 
be called the active variety, this is the opposite or passive form. 
It is heavier than the former, red in color, does not shine in the 
dark, nor melt at the heat of boiling water. It exhales no vapor 
or odor ; oxidizes but very slowly in the air, does not change oxygen 
into ozone, is chemically indifferent toward other elements, may 
be handled with impunity, or carried exposed in the pocket, and 
is not poisonous when administered in doses a hundred times 
greater than would be fatal in the common form (G. Wilson). 
At 500° it is reconverted into the active form and bursts into flame. 

672. Uses — The chief use of phosphorus is in the manufacture 
of friction matches, and vast quantities are consumed in this way 
among all civilized nations. In making matches the blocks are 
sawn by machinery, and the ends first tipped with sulphur, and 
then with an emulsion of phosphorus in glue, with a little saltpetre, 
oxide of manganese, or chlorate of potash ; bodies all rich in ox- 
ygen. The manufacture is not only dangerous from the explosive 
nature of the materials used, but from the corrosive phosphoric 
vapors, which produce among the laborers the distressing disease 
known as caries of the lower jaw. An attempt has been made to 
avoid these evils by the use of passive phosphorus in this manu- 
facture, but as yet with only partial success. 

673. Office in Nature. — The part played by phosphorus in the 
scheme of nature is of the highest interest. Existing, combined 

670. How many are its allotropic forms? What are they? 671. What are the 
properties of passire phosphorus? 672. For what is phosphorus used? Describe 



PHOSPHORUS AND ITS COMPOUNDS. 



265 



with lime, in the primitive and volcanic rocks, by their gradual 
decay in the course of ages, it passes into the soil. The plants, 
with their thousand rootlets sucking up the soluble extract of soil, 
obtain compounds of phosphorus, which rise with the sap to the 
leaf. It is maintained by some that a portion of its compounds is 
here decomposed, the phosphorus being set free and thrown into 
the passive state by the chemical influence of the sunbeam ( 372 ). 
However this may be, it is stored up in the seeds which are des- 
tined to nourish man and the higher animals. One portion is em- 
ployed to build up the bony structure, while another forms a large 
constituent of the nervous system and brain. What the precise 
office of phosphorus in the brain may be we cannot say, but that 
it performs some high duty in the reactions of the mind with its 
organ, is manifest from the fact that after prolonged brain-exercise 
there is a rise in the proportion of phosphoric products in the 
liquid excretion. 

674. — Phosphoric Acid, P0 5 (Phosphoric Anhydride). — When 
phosphorus is burned in dry oxygen, Fig. 241, the 
dense, white vapors which are formed condense 
upon the glass in snow-like flakes. This is phos- 
phoric anhydride. It has a powerful attraction for 
moisture, absorbing it from the air, or, if brought 
into contact with water, seizing it with such vio- 
lence as to emit a hissing sound. Phosphoric acid 
is thus formed, which always contains water in its 
composition. By evaporation, a vitreous-looking 
substance is produced, known as glacial phos- 
phoric acid. Its solution is very sour. 

675. The intensity of the attraction of phosphorus 
for oxygen may be strikingly shown by directing a 
stream of the gas against a small piece of phosphorus 
at the bottom of a vessel of warm water, when a bril- 
liant combustion will be observed beneath the liquid 
Fig. 242. 

676. Phosphoric acid is procurable from bones by 
the action of sulphuric acid, which displaces it by seiz- 
ing the lime, or by the direct oxidation of phosphorus 



Fig 241. 




Combustion 
of Phosphorus. 



Fig. 242. 




Under Water. 



the process. "What is said of its dangers? 673. Whence do plants obtain their 
phosphorus ? What are its offices in the animal system ? Its relations to mental 
action ? 674. What is phosphoric anhydride ? Glacial phosphorus ? 67o. How ia 

12 



266 INORGANIC CHEMISTRY. 

by nitric acid. It combines with water in three proportions, 
forming 

Monobasic or metaphosphoric acid, HO, P0 5 . 

Bibasic or pyrophosphoric acid, 2HO, P0 5 . 

Tribasic or common phosphoric acid, 3HO, P0 5 . 
These three acids give rise to three series of salts. 

677. Phosphide of Hydrogen, PH 3 (Phosphuretted Hydrogen), — 
This is a colorless gas, with a very offensive odor, is poisonous when 
inhaled, and produced in small quantities by the decay of animal 
matter. It may be prepared by heating small fragments of phos- 
phorus with a strong solution of caustic potash in a retort. The 
end of the retort tube dips beneath water, and as the gas passes 
out in bubbles, it rises to the surface and takes 
fire spontaneously. If some pieces of the phos- 
phide of calcium are thrown into a glass of 
water, the same thing takes place. Double de- 
composition with the water produces phosphu- 
retted hydrogen, which ignites at the surface 
and forms beautiful wreaths of vapor, Fig. 243. 
The other phosphides of hydrogen are of little 
interest. 

678. Phosphorus combines with chlorine so 
3 energetically as to take fire. It also forms nu- 
merous compounds with iodine, bromine, nitro- 
gen, and sulphur, but they are comparatively unimportant. 




CHAPTEE XII. 

THE HTALOGENS OR GLASS FORMERS. 

§ I. Silicon and its Compounds. 

SILICON. 

Sym. Si. Bquiv. 14. 

679. Silicon.— This element is never found free in nature, 
but exists very extensively in the mineral crust of the earth in 

its intense attraction for water shown? 676. How is it obtained from bones? 
Whence arise the three series of salts ? 677. What are the properties of phosphu- 



SILICON AND ITS COMPOUNDS. 267 

combination with oxygen, forming silica. It has three allotropic 
states: first, amorphous silicon—a brown powder; second, a 
variety resembling graphite; and third, a crystalline form. It 
holds an equivocal place in classification, some ranking it with the 
metals. It is difficult to separate, and is of no importance except 
to the scientific chemist. 

680.— Silica, Si0 2 {Silicic Acid, Silex, Sand). — This is a com- 
pound of silicon and oxygen, the proportions of which are unset- 
tled. Beezelius held that it is Si0 3 , analagous to sulphuric acid, 
and this view has been generally accepted. But later chemists 
consider it as Si0 2 , or analogous to carbonic acid. 

681.— Silica is the most abundant of mineral substances. Its 
purest condition is that of quartz, in which it forms hexagonal 
crystals terminated by six-sided summits, Fig. 244. If 244 

this mineral is heated to redness and quenched in water, >^ 
it is reduced to a fine, white, tasteless, gritty powder, yfj \>\ 
which is nearly pure silica. The chief constituents of 
all sandstones is silica, and it occurs in large proportion 
in many other rocks ; these, by decomposition, yield the 
silicous principle or sand of soils. The common flint 
and many valuable stones, as amethyst, agate, chalce- 
dony, carnelian, jasper, opal, and sardonyx, consist of Quartz Oys- 
silica, variously colored by other substances. 

682. Solubility. — In pure water, and in all acids, except the 
hydrofluoric, it is insoluble, but it is dissolved by alkaline solu- 
tions. Hence, all natural waters which contain alkaline carbonates 
hold also in solution a little silica. If wood be present in such 

- waters, as it decays, the particles of silica are deposited in place 
of those that escape, and thus a copy of the wood in stone, or a 
1 'petrifaction, is produced. 

683. It is an Acid. — Though so insoluble and inert, silica is 
really an acid, combining with bases, and forming silicates which 
are true salts. By the intense heat of the oxyhydrogen flame it is 
melted into a pure glass, and may be spun out into threads. But 
| when mixed with alkalies it melts at a lower temperature, combin- 
ing with them to form ordinary glass. The most abundant min- 
|" : 

retted hydrogen? How is it obtained? 678. Other compounds of phosphorus? 
|679. Where is silicon found? "What are its allotropic forms? 6S0. "What is the 
composition of silica ? 681. What is the purest silica ? What is said of its abun- 
dance ? 682. Its solubility ? How are petrifactions formed ? 683. What are sili- 



268 INORGANIC CHEMISTRY. 

erals, mica, feldspar, hornblende, serpentine, &c, which form the 
granitic, and many other rocks, are silicates of the alkalies and 
alkaline earths ; — like glass, they are also salts. 

684. Silica of Soli. — At common temperatures carbonic acid is 
stronger than silicic ; hence, upon many of the silicates the air 
exerts a destructive agency. Its carbonic acid slowly unites "with 
their bases, setting the silica free, thus forming one of the disinte- 
grating forces by which rocks are reduced to the condition of soil. 
At the moment of its liberation it is soluble in water. In this 
way, but still more powerfully by the action of alkalies, silica is 
dissolved by the water of soils, and, entering the roots of plants, 
performs an important office in giving stiffness and strength to the 
stalks of grains and grasses. 

685. Soluble Glass.— If 8 or 10 parts of carbonate of soda or 
potash are mixed with 12 or 15 parts of sand and 1 of charcoal, on 
being heated they melt, and form a mass resembling ordinary 
glass ; but it entirely dissolves in hot water. This is known as 
soluble glass, and when applied to wood and other substances an- 
swers the protective purpose of a varnish or paint. 

686. Its Colloidal Form. — If to a solution of soluble glass, 
chlorohydric acid be added, it neutralizes the alkali, and the silica 
separates as a transparent jelly — a fine example of the colloid 
state (83). It is a hydrate of silica, and is insoluble in water or 
acids. This gelatinous state may be continued by keeping it 
moist, but as soon as it is deprived of water it falls to a gritty 
powder. 

687. Fluoride of Silicon, SiF 2 (Fluosilicic Acid).— -This is a 
colorless gas produced when fluohydric acid is liberated in contact 
with silica. When passed into water the gas is decomposed, the 
silica becoming gelatinous, and the water a solution of hydrofluo- 
silicic acid, HF, SiF 2 . 

688. Silicates are salts of silica, and form a large class of nat- 
ural minerals. Most of them are fusible ; some, however, melt at 
only very high temperatures. They are all insoluble in water except 
the silicates of the alkalies. Those artificial silicates which are 
of interest in the arts will be noticed when speaking of their 
respective bases, 

cates ? Give examples. 684. What is the action of carbonic acid upon silicates ? 
What is the office of silica in plants ? 685. What is soluble glass ? 686. Describe 
its colloidal form. What is it ? 687. What is fluoride of silicon ? 688. Stato the 



GENERAL PROPERTIES OF THE METALS. 269 

§ II. Boron. 
Syni. B. Equiv. 10.9. 

689. Boron is a rare substance always found in combination 
with oxygen, as boracic acid. It strongly resembles silicon, and, 
like it, is capable of assuming three allotropic states. 

690. Boracio Acid, B0 3 . — This is found as a natural constitu- 
ent of several minerals, but the principal supply is derived from 
the lagoons of Tuscany. Here, the acid issues from the earth along 
with jets of steam, and is collected by throwing the jets into water. 
The acid is afterward separated from the water by evaporation in 
leaden pans so arranged that they are heated by the vapors as 
they escape from the earth. It is deposited in white, scaly crystals, 
which are purified by repeated crystallizations. These crystals 
have a glassy appearance, and are soapy to the touch. They dis- 
solve much more readily in boiling than in cold water, and form a 
solution having feebly acid properties. 



CHAPTER XIII. 

THE METALLIC ELEMENTS. 

§ I. General Properties of the Metals. 

691. The metals form the largest division of the chemical ele- 
ments, and are distinguished by certain characteristics which they 
manifest in very different degrees. They have all a peculiar shining 
appearance, called the metallic lustre. Most metals, however, may 
be obtained in conditions free from this lustre, while some bodies 
which are not metals, as iodine and plumbago, have also a metallic 
brightness. They vary in color ; several, as silver and platinum, 
are white, with tints peculiar to each ; others, as lead and tin, are 
bluish ; iron and arsenic are grayish ; calcium and barium a pale 
yellow ; gold a bright yellow, and copper red. 

692. Hardness, Brittleness, Tenacity. — In hardness the metals 
exhibit wide differences ; steel scratches glass, while potassium is 

Vioperties of the silicates. 689. "What is boron? 690. How is boracic acid ob- 
tained ? 691. How are the metals distinguished ? What of their colors ? 692. How 



270 INORGANIC CHEMISTRY. 

soft as wax. Some, as bismuth and antimony, are so brittle that 
they may be easily crushed in a mortar, while to pulverize gold or 
copper requires immense force. Their tenacity, which is deter- 
mined by the amount of weight which wires of equal diameter 
will support, is also various. If lead be taken as 1, copper is IT 
and iron 26. Heat generally diminishes the tenacity of metals, 
but in the case of iron and gold it increases it up to 212°. 

693. Malleability and Ductility. — Malleable metals are those 
which may be hammered into thin leaves. Gold heads the list, and 
has been reduced to a film the 20 o?o oo 0I * an mcn m thickness. 
In ductility, or capability of being drawn into wire, platinum 
stands first. Wollaston produced wire from it but 20^00 °f an 
inch in diameter. The foregoing properties in each case vary with 
the texture of the metal. 

694. Specific Gravity. — In this respect also there are great 
differences. While platinum is 22 times heavier than water, lith- 
ium is but little more than half as heavy as that liquid. The 
lightest metals have the strongest affinity for oxygen. 

695. Fusibility.— The range of properties is here most remark- 
able. "While mercury remains fluid at 39°, potassium and so- 
dium fuse below the boiling point of water ; silver and gold melt 
at a red heat, iron at a white heat (2,786°), and platinum only at 
the intense, but undertermined heat of the oxyhydrogen blow- 
pipe. 

696. Volatility. — Mercury vaporizes at 662°, and several metals 
are so volatile that they may be distilled from their compounds. 
Lead is largely volatilized, and copper slightly so in the smelling 
furnaces, and even gold is dissipated in vapor in the focus of a 
powerful burning glass. Some of the metals emit odors ; arsenic 
gives the smell of garlic, while iron, tin, and copper by friction 
give forth distinctive odors. 

697. Conduction of Heat and Electricity. — The metals are ex- 
cellent conductors of heat and electricity, but vary in this respect. 
When separated from their compounds by electrolysis, they appear 
at the negative pole, and are hence electro-positive. It is remark- 
able that the vapors of the metals are non-conductors of electricity. 

698. The metals occur in nature in three states. First, some 

do they vary in hardness, brittleness, and tenacity? 693. In malleability and 
ductility? 694. Specific gravity? Relation to affinity? 695. How do they 
differ in fusibility ? 696. In volatility ? 697. What is their relation to heat and 



GENERAL PEOPEETIES OF THE METALS. 271 

of them, as gold, silver, platinum, and mercury, are often found un- 
combined, and are said to occur in the native state. Second, 
many are found alloyed with each other, as gold and silver with 
mercury ; but usually they occur in combination with the metal- 
loids, for which they have a strong attraction. These compounds 
are known as metallic ores. 

699. Distribution. — The soil and rocks beneath us, as has been 
stated, consist of metallic oxides, but the chief metals used in the 
arts are not so widely disseminated. They are found in various 
places and at various depths in the earth, in the form of seams, 
beds, or mineral veins. Fissures and openings among the older 
or fire-formed rocks often occur filled with ores, and are called 
lodes. The thickness and direction of veins are various, the most 
productive generally occurring near the junction of two dissimilar 
kinds of rock. It is supposed they are ' accumulated there in 
consequence of slow voltaic actions which have been going on 
through uncounted ages, and which have been occasioned by 
differences in chemical composition of the two contiguous rocks.' 
(Millee.) The ores are procured by excavating shafts in the earth, 
cutting horizontal or inclined galleries, and by picking, wedging, 
and blasting out the minerals. 

700. Treatment of Ores. — This is first mechanical, then chem- 
ical ; the more valuable the ore, the more care does its manage- 
ment require, but the operations differ widely in different cases. 
The ores of lead and tin are dressed as follows : when brought to 
the surface, they are sorted, the purest lumps being set aside for 
the smelting furnace. The residue is then broken by hammers, 
and again sorted. The rougher portions are then crushed between 
revolving cylinders and the product passed through coarse sieves ; 
while the finer part is agitated in water by the hand process of 
jigging. The crushing is completed in the stamping mill, which 
consists of upright, wooden beams, shod with iron and lifted by 
steam or water power, which are allowed to fall upon the ore. 
The products are repeatedly washed, and the powdered ores settle 
in layers according to their specific gravities. 

701. Roasting Ores. — After ores have been prepared mechan- 
ically, they are subjected to chemical treatment, which is twofold 

electricity? 698. In what three states are the metals found ? 699. How do they 
usually occur ? How are the veins formed ? How worked ? 700. How are lead 
and tin ores dressed ? 701. When are metals roasted ? How is it done? "When is 



272 



INORGANIC CHEMISTRY. 



Fig. 245. 




— roasting and reducing. If they contaiD volatile products, as 
sulphur or arsenic, which may be removed by oxidation or heat, 
they are first roasted. This is done in an oven-shaped furnace, 
called a reverberatory, Fig. 245. The fuel is placed at one end, and 

the heated gases and flame are re- 
verberated, or thrown down from 
the arched roof of the furnace upon 
the ore, which is distributed over 
its bed. In this way ores are ox- 
idized. If they contain sulphur, it 
burns off and escapes as sulphurous 
acid, while arsenic is carried away 
as arsenious acid. Sometimes, as in 
the case of lead, the metal is at 
once procured by the operation of 
roasting. In other instances it is 
changed to the state of oxide, and then requires another process to 
set it free. 

702. Reduction or Smelting of ores is 
the chemical process of deoxidation. It is 
effected by heating them to a high tempera- 
ture in contact with substances which take 
the oxygen from the metal by superior 
affinity. Carbon is the chief deoxidizing 
agent, and removes the oxygen in the form 
of carbonic oxide and carbonic acid. For 
the removal of various earthy impurities, sub- 
stances are employed termed fluxes, which, 
combining with them, melt and flow off as 
crude glass or slag. For laboratory opera- 
tions with the metals, small furnaces are indis- 
Laboratory Furnace, pensable, such as those represented in Fig. 246* 



Reverberatory Furnace. 



Fig. 246. 




§ II. Theory and Constitution of Salts. 

703. Salts result from the union of non-metallic elements with 
the metals ; they are therefore to be considered as compounds of 
the metals; It has been stated that salts are formed by the union 



another process required ? 702. What is smelting ? How effected ? For what is 
carbon used ? What is the use of fluxes ? 703. How are salts to bo considered ? 



THEOEY AND CONSTITUTION OF SALTS. 273 

of acids and bases, but a more complete account of their consitu- 
tion is now necessary. 

704. Two Kinds of Acids and Salts. — When oxygen was dis- 
covered it was found by Lavoisiek to enter largely into the com- 
position of acids ; it was therefore believed to be the universal 
acidifying principle, and given a name which signifies acid-former. 
But it was afterward found that there are powerful acids, as the 
chlorohydric and iodohydric, which contain no oxygen at all, their 
common principle being hydrogen. Hence two kinds of acids 
were recognized, oxacids and hydracids. 

705. In like manner it was at first supposed that all salts were 
double compounds, acid united to base, as sulphuric acid to potash, 
KO, S0 3 . But it was at length discovered that this composition 
represents but a part of the salt family, and if adopted would ex- 
clude common salt itself, the very substance from which the term 
salt was derived. For, although common salt is produced by the 
addition of an acid and a base, chlorohydric acid to soda, yet there 
is not a simple union of the two binary compounds, but a double 
decomposition : the acid and the base are each split, and two com- 
pounds result ; thus NaO + HCl = NaCl + HO. That is, when 
these substances are brought together, chloride of sodium and water 
are formed. Hence two kinds of salts are recognized, oxysalts and 
the haloid salts, or those which resemble common salt, from hales, 
the sea. But it has been latterly maintained that there is only 
one type of acids and one of salts. Davy started the hypothesis 
that all acids are properly hydracids, and all salts binary. 

706. The Later View of Acids. — It is well known to chemists 
that when the oxacids, sulphuric, nitric, and phosphoric, are deprived 
of water, they no longer possess true acid properties. Sulphuric an- 
hydride does not redden litmus, nor corrode the fingers ; but if 
water be added, it instantly becomes a powerful acid. Now, as hy- 
drogen is present in all the hydracids, and as the oxygen compounds 
only become acid by the addition of water which contains hy- 
drogen, it is assumed that not oxygen, but hydrogen is the universal 
acidifying principle ; and if there is but one acid-former, there is 
probably but one type of acids. The elements which combine with 
hydrogen to form acids are called radicles, as chlorine, iodine, &c. 

704. What was the early idea of oxygen ? What is now known ? 705. What was 
the first idea of salts ? What was at length discovered ? Constitution of common 
salt. What is Davy's hypothesis ? 706. Why has hydrogen been regarded as the 

12* 



274 INORGANIC CHEMISTRY. 

707. In speaking of cyanogen, it was stated that there is 
a class of compound bodies of which that substance is a type, which 
play the part of simple elements, and are called compound radicles. 
Cyanogen, NC 2 , combines directly with hydrogen (like the simple 
radicle chlorine), to form cyanohydric acid, HNC 2 . Now it is 
assumed that the oxacids contain compound radicles in the same 
way ; and if this be admitted, the whole case is simplified. It is 
claimed that in sulphuric acid there is the radicle sulphion S0 4 ; in 
phosphoric acid, phosphion P0 6 , and in nitric acid, nitration N0 6 . 
These radicles unite with hydrogen, and thus the oxacids are 
binary. Sulphuric acid is sulphionide of hydrogen. The change 
is simple. 

OLD YIEW OF AOIDS. NEW VIEW. 

Phosphoric acid, HO, PO 5 . H, P0 6 , analogous to H, Cy. 
Sulphuric acid, HO,S0 3 . H, S0 4 , " " H, CI. 

Nitric acid, HO, N0 5 . H,N0 6 , " " H,Br. 

Hence we arrive at the following definition : An acid is the 
hydrogen compound of a simple or compound radicle which pos- 
sesses the power of neutralizing dases; its general formula oeing 
HR {hydrogen and radicle.) 

708. Later View of Salts. — From this point of view the com- 
position of salts is also simplified ; one type of acids gives us also 
one type of salts. By replacing the hydrogen of chlorohydric 
acid, HC1, by sodium, we get common salt, NaCl. By replacing 
the hydrogen of cyanohydric acid by potassium, we get the salt 
cyanide of potassium, HNC 2 . And so by replacing the hydrogen 
of sulphionide of hydrogen by iron we get sulphionide of iron, 
FeS0 4 , instead of the old sulphate, FeO,S0 8 . On this view we 
may define a salt to be the compound formed oy replacing the hy- 
drogen of an acid ly a metal ; and the general formula for a salt 
is MR {metal and radicle.) (For diagrams rendering this sub- 
ject easy of comprehension, see Author's Chemical Chart and 
Atlas.) 

709. Estimate of the Hypothesis.— Although the foregoing 
hypothesis is ingenious and useful, and is perhaps growing in 
favor with progressive chemists, yet upon close examination, it is 

acidifying principle? What are radicles? 707. Compound radicles? Explain 
the new view of acids. What is the definition of an acid by this view ? 708. Ac- 
cording to this, how are salts formed ? Give the definition of a salt. 709. What 



THEORY AND CONSTITUTION OF SALTS. 275 

found liable to objection, and, as remarked by Peof. Miller, 
cannot be considered as a correct representation of the composi- 
tion of a salt under all circumstances. A salt, wben once formed, 
may be regarded as a whole ; it can no longer be looked upon as 
consisting of two distinct parts, but as a new substance maintained 
in its existing condition by the mutual action of all the elements 
which compose it. These different elements are not all united 
with each other in every direction with an equal amount of force. 
As a crystal cleaves in different directions as the force is differ- 
ently applied, so a salt may split up into different simpler sub- 
stances, according as the chemical force is applied one way or 
another. The probability therefore is, that neither the old nor the 
new view is absolutely correct, but that each may in turn well re- 
present the salt when subjected to the influence of different 
forces. 

710. Sulpho-Salts. — Sulphur is analogous to oxygen in chemical 
relations ; and as there are oxy salts, so there is also a class of sul- 
pho-salts, exactly corresponding to them in constitution. 

711. Normal Salts. — The term normal salts has been applied 
to all those in which there is an atom of acid for each atom of 
oxygen in the base. Carbonate of potash, KO, C0 2 , is an example. 
Where the base consists of a sesquioxide containing three atoms of 
oxygen, it requires three atoms of acid to form a normal salt. For 
example, alumina, Al 2 , O3, requires three atoms of sulphuric acid 
to form a normal sulphate of alumina, AL, 3 , 3S0 3 . 

712. If a solution of oxalic acid be added to that of potash in 
equivalent proportions, a neutral salt is formed. If this be re- 
dissolved, and another proportion of oxalic acid be added, it unites 
with the salt already formed, and an acid or super-salt is produced 
which reddens litmus and crystallizes in a different form from the 
first. Basic or sub-salts have an opposite structure — the base pre- 
dominating over the acid. It has been stated that water in combi- 
nation plays the part of both acid and base. "With bases it unites 
as a feeble acid, and with acids as a feeble base. When one atom 
of water is combined with one of acid, it forms a monobasic acid ; 
if two of water, a bibasic acid ; and if several, a polybasic acid. 
Hence, by replacing the water of polybasic acids by metallic bases, 

does Prof. Miller say of this theory? 710. What are sulpho-salts ? 711. What 
are normal salts ? 712. What is a neutral salt ? A super-salt ? A sub-salt ? When 



276 INORGANIC CHEMISTRY. 

we get sub-salts or basic salts. If different bases combine with poly- 
basic acids, they produce double salts. 

713. In crystallizing from aqueous solutions salts combine with 
a definite proportion of water, which is contained in the crystal as 
water of crystallization. Alum crystals contain nearly one half 
their weight of water. Certain crystals (Glauber's salts, for exam- 
ple), if exposed to the atmosphere, part with their combined water 
by evaporation, lose their brilliancy and crumble to a white pow- 
der ; this is called efflorescence. Other salts when rapidly crystal- 
lizing confine mechanically in their texture a portion of the mother 
liquor, causing them when expanded by heat to explode with a 
crackling noise, which is termed decrepitation. Others, when ex- 
posed to the air, absorb water and become semi-liquid, the process 
being called deliquescence. 

The salts that have been produced are already numbered by 
thousands, and there is no end to their multiplication. We shall 
have space to notice but a few, and those briefly. 



CHAPTER XIY. 

METALS WHICH DECOMPOSE WATER AT ORDINARY 
TEMPERATURES. 

714. Authors vary in their classification of the metals, but 
they are usually arranged according to their affinity for oxygen. 
We shall divide them into three groups : first, metals which decom- 
pose water at common temperatures ; second, metals which on?y 
decompose water at a red heat ; third, metals which cannot de- 
compose water at all. The first group comprises nine elements, as 
follows : — 



Potassium, 

CAESIUM, 

BuBIDIUM, 

SODIUM, 

Lithium, 
Barium, 
Strontium, 
Calcium, 

Magnesium. 



The first five metals of this group, 
when oxydated, produce alkalies, and are 
therefore called metals of the alkalies. The 
oxides of the remaining four are alkaline, 
though in a less degree, and have also an 
earthy appearance ; hence they are termed 
metals of the alkaline earths. 



is an acid said to "be monobasic ? When bibasic ? When polybasic ? 713. What 
is water of crystallization ? What is effervescence ? Decrepitation ? Deliques- 



METALS OF THE ALKALIES. 277 

§ I. Metals of the Alkalies. 

1. POTASSIUM AND ITS COMPOUNDS. 
Potassium. Sym. K {Kalium). Uquw. 39. Sp. Gr. 0.855. 

715. Potassium was discovered by Sir Humpheey Dayt in 1807, 
together with sodium, barium, strontium, and calcium. Before 
that time the alkalies and alkaline earths had been considered as 
simple bodies, and the discovery of their compound nature forms 
an interesting era in chemical science. Davy obtained this metal 
by subjecting moistened potash to the action of a powerful voltaic 
battery ; the positive pole gave off oxygen, and metallic globules 
of pure potassium appeared at the negative pole. 

716. It is never found free in nature, but occurs abundantly 
in rocks and soils combined with oxygen ; as potash. It is usually 
obtained by the action of charcoal upon carbonate of potash at a 
very high temperature. The carbonate is decomposed, the free 
carbon seizing the oxygen of the potash and escaping as carbonic 
oxide, while the metal distils over into suitable condensers, 

KO,C0 2 + 2C = K + 3CO. 

717. Properties. — Potassium at common temperatures is a silver- 
white metal, and so soft that it may be moulded like wax. It has 
a powerful affinity for oxygen. If thrown upon the surface of 
water, instant decomposition takes place 

Tig. 247, the potassium uniting with the 
oxygen to form potash. The liberated hy- 
drogen, together with a small quantity of 
volatilized metal, is ignited by the heat 
evolved during the decomposition, and com^u^^tassium. 
burns with a beautiful lilac flame as the 
globule floats about on the surface of the liquid. Potassium de- 
composes nearly all compounds containing oxygen, if brought in 
contact with them at high temperatures, and many even at ordi- 
nary temperatures. Hence, to preserve it pure, it is kept in naphtha, 
a liquid containing no oxygen. 




cence? 714. How are tho metals classified? How is group first divided? 715. 
When and by whom was potassium discovered? By what means? What was 
the effect of the discovery? 716. How does it occur in nature? How is it 
obtained ? 717, What aro its properties ? Why is it kept in naphtha ? 



278 INORGANIC CHEMISTRY. 

71 8. Protoxide of Potassium, KO {Potash). — This, the most im- 
portant compound of potassium, is always formed when the metal 
comes in contact with free oxygen. It has a powerful attraction 
for water, absorbing it with avidity when exposed to a moist at- 
mosphere, and forming a hydrate, or caustic potash, KO, HO. This 
is generally procured by the action of caustic lime in a boiling so- 
lution of carbonated potash. The lime unites with the carbonic 
acid of the potash, forming insoluble carbonate of lime, which sub- 
sides. The clear liquid, containing the potash in solution, is then 
drawn off and concentrated by evaporation. If the heat be 
continued to a point little short of redness, the liquid flows 
without ebullition, and may then be run into moulds, where 
it solidifies on cooling, forming the small, grayish-white sticks 
of commerce. 

719. Potash possesses all the properties of the alkalies in a pre- 
eminent degree. It saturates the most powerful acids, changes 
vegetable yellows to brown, restores the blues discharged by 
acids, and decomposes animal and vegetable substances, whether 
living or dead. It is used in medicine to cauterize and cleanse 
ulcers and foul sores; hence its name, caustic potash. If a 
solution of potash be shaken in a bottle with any fixed oil, the 
two unite, forming a soap. This accounts for the soft greasy 
feel it has when touched by the fingers, as it decomposes the 
skin and forms a soap with its oily elements. "When taken into 
the system, potash acts as a powerfully corrosive poison. Its 
active chemical character renders it an indispensable reagent in 
the laboratory. 

720. Iodide of Potassium, KI (Hydriodate of Potash).— -This 
may be formed by adding iodine to a solution of potash, and 
gently warming until the solution assumes a brown tint. It is a 
very soluble, white solid, which crystallizes in cubes, and is much 
used in medicine. 

721. Carbonate of Potash, KO,C0 2 . — Potash exists in plants 
in combination with various organic acids. When the plant is 
burned, these combinations are broken up ; the organic acids are 
decomposed into carbonic acid and water, and the liberated pot- 
ash unites with a portion of the carbonic acid formed by combus- 

718. What is potash? Hydrate of potash? How is caustic potash obtained? 

719. "What are its properties ? What is its action with oils ? Its uses in medicine ? 
In the laboratory ? 720. What is iodide of potassium ? Its uses ? 721. How is 



METALS OF THE ALKALIES. 279 

tion, thus producing carbonate of potash. This is a highly alka- 
line, deliquescent salt, and is used largely in the manufacture of 
soap and glass, in preparing caustic potash, &c. It is also an im- 
portant reagent in the laboratory, and is a most valuable fertilizer. 
This salt rarely forms less than 20 per cent., and sometimes more 
than 50 per cent, of the weight of wood ashes. The ashes of dif- 
ferent plants, and even different parts of the same plant, yield it 
in varying amounts. Wood ashes furnish the principal source 
of the carbonate of potash of commerce, from which it is obtained 
by leaching them and boiling the solution to dryness in iron pots. 
The residue is called potashes, and these, when calcined, afford the 
impure carbonate known as pearlash. Potash, or pearlash, there- 
fore represents the readily soluble portion of wood ashes, and con- 
sists chiefly of carbonate of potash with small amounts of carbon- 
ate of soda and common salt. 

722. Bicarbonate of Potash, KO, 2C0 2 .— This is formed by 
passing carbonic acid through a strong solution of carbonate of 
potash, which combines with a second equivalent of the acid. It 
is employed as a source of potash in the formation of many of its 
other compounds, and is also used for making effervescing draughts 
by adding citric or tartaric acid to its solution, which, combin- 
ing with alkali, sets the gas free. 

723. Nitrate of Potash, KO,N0 5 (Nitre, Saltpetre).— -This salt 
occurs as a native product in the earth of various districts in the 
East Indies, and is separated therefrom by leaching the soil, and 
allowing the nitre to crystallize. It is artificially formed by heap- 
ing up organic matter with lime, ashes, and soil, and keeping the 
mass well moistened with urine for a period of two or three years, 
when the heap is lixiviated and the salt crystallized out. Besides 
these sources, nitre occurs in the sap of certain plants, such as the 
sunflower, tobacco plant, &c. 

724. Mtre dissolves in about three times its weight of cold 
and one third its weight of boiling water. It is rich in oxygen, 
and when thrown upon burning charcoal is decomposed and defla- 
grates violently. Paper dipped in this solution, and dried, forms 
what is known as touch paper. "When ignited, it burns slowly and 

carbonate of potash obtained ? State the properties and uses of the salt t How 
do its proportions vary in different ashes ? What is pearlash ? For what used ? 
722. What is bicarbonate of potash? Its uses? 723. How does nitrate of potash 
occur? Explain its artificial formation. From what other sources obtained? 



280 INORGANIC CHEMISTRY. 

steadily until consumed ; hence its use in lighting trains of gun- 
powder, fireworks, &c. Nitre has a cooling, saline taste and 
strong antiseptic powers. Owing to the latter quality it is 
used extensively in packing meat, to which it imparts a ruddy 
color. It is chiefly consumed, however, in the manufacture of 
gunpowder ; the large amount of oxygen it contains, and the 
feeble affinity by which it is held, adapting it for sudden and 
rapid combustion. 

725. Gunpowder is an intimate mechanical mixture of about 
1 part nitre, 1 part sulphur, and 3 parts charcoal. These propor- 
tions, however, vary somewhat in different countries, as well as in 
different sorts of powder. More charcoal adds to its powei\ but 
also causes it to attract moisture from the air, which of course in- 
jures its quality. For blasting rocks, where a sustained force, 
rather than an instantaneous one, is required, the powder contains 
more sulphur, and is even then often mixed with sawdust to re- 
tard the explosion. 

726. Manufacture. — The nitre, sulphur, and charcoal, having 
been ground and sifted separately, are thoroughly mixed and then 
made into a thick paste with water. This is ground for some 
hours under edge stones, after which it is subjected to immense 
pressure between gunmetal plates, forming what is known as 
press-cake. These cakes are then submitted to the action of toothed 
rollers, whereby the granulation of the powder is effected. The 
grains thus formed are sorted into different sizes by means of a 
series of sieves, and thoroughly dried at a steam heat. The last 
operation, that of polishing, is accomplished in revolving barrels, 
after which the powder is ready for market. The heavier the 
powder, the greater is its explosive power. Good powder should 
resist pressure between the fingers, giving no dust when rubbed, 
and have a slightly glossy aspect. The explosive power of gun- 
powder is due to a sudden formation of a large volume of nitrogen 
and carbonic acid gas ; one volume of the powder giving about 
1,800 volumes of vapor. Fireworks contain nitre as a chief in- 
gredient, mixed with charcoal, sulphur, ground gunpowder, and 
various coloring substances. 

727. Chlorate of Potash, KG, C10 5 .— This may be formed by 

724. What is touch paper ? For what used ? What are the uses of nitre ? 725. 
What is gunpowder ? How may its properties be varied ? 726. Describe its man- 
ufacture ? How may good powder be distinguished ? To what is the explosive 



SODIUM AND ITS COMPOTOTDS. 281 

passing chlorine gas through a solution of carbonate of potash. 
Chlorate of potash is soluble in water, has a taste resembling that 
of nitre, melts at about 700°, and, if heated above that tempera- 
ture, parts with its oxygen. It is used in the manufacture of 
lucifer matches, in certain operations of calico printing, and as a 
source of oxygen. 

2. SODIUM AND ITS COMPOUNDS. 

Sodium, Sym. Na. (Natrium). Equiv. 23. Sp. Gr. 972. 

728. Sodium closely resembles potassium in both appearance 
and properties. It is prepared in the same manner from its car- 
bonate, and like potassium, must be kept in naphtha to prevent its 
oxidation. "When freshly cut it presents a silvery appearance, and 
if cast upon hot water bursts into a beautiful yellow flame, and is 
converted into oxide of sodium, or soda ; the same reaction taking 
place as in the case of potassium. Sodium is a very abundant 
metal, constituting more than two fifths of common salt, and exist- 
ing as a large ingredient of rocks and soils. 

729. Oxide of Sodium, $TaO (Soda). — This compound of so- 
dium strongly resembles the corresponding one of potassium, 
though its properties are somewhat less marked. For commercial 
purposes it is chiefly obtained from common salt. Soda, like pot- 
ash, attracts moisture from the air, forming a hydrate. It results 
from recent discoveries in spectrum analysis (346), that com- 
pounds of sodium are almost everywhere' diffused. They are 
found in the atmosphere, and in particles of dust ; indeed it seems 
that we can hardly touch any substance without imparting to it 
a little soda salt from our hands. 

730. Chloride of Sodium, KaOl (Common Salt).— This well 
known substance needs little description. It exists in great 
abundance both in solution and as a solid. Sea water contains in 
every gallon about 4 ounces of salt. Estimating the ocean at an 
average depth of two miles (Lyell), the salt it holds in solution 
would, if separated, form a solid stratum 140 feet thick. Saline 
springs in various localities in this country yield enormous quan- 
tities of salt by the process of evaporation. The springs in the State 

power due? What is the composition of fireworks? 727. Give the composition 
and properties of chlorate of potash. For what is it used ? 728. What is sodium ? 
State its properties. 729. What is the composition of soda ? Its sources ? 730. 



282 



INORGANIC CHEMISTRY. 



of New York alone furnish an annual supply of about 6,000,000 
bushels. As a solid it occurs in extensive beds in various local- 
ities in Europe. The celebrated bed at Wielitzka, Poland, is said 
to be 500 miles long, 20 miles broad, and 1,200 feet thick, con- 
taining salt enough to supply the entire world for thousands 
of years. 

731. Salt exists in small quantities in plants, and sometimes 
promotes their growth by being applied to the soil. It is also an 
ingredient of animal bodies, being contained in the blood. It forms 
an important constituent of the food of both man and beast, an 
adult consuming (as estimated by Pereiea) about five ounces per 
week. 

732. Common salt is readily sol- 
uble alike in hot or cold water, and 
usually crystallizes in cubes. A pe- 
culiar-shaped crystal, or aggregation 
of crystals, is often formed when the 
salt is allowed to crystallize from 
concentrated solutions. A small 
cube is first formed which sinks so 
as to bring its upper surface on a 
level, or a little below the surface 
of the water, Fig. 248. Other cubes 
form on this, and as the mass sinks, 
still others are deposited, each layer 
being attached to the upper and 
outer edge of the layer next beloiv, 
until a form like that seen in Fig. 
252 is obtained. 

733. Salt is used for packing and 
preserving meat, as it prevents pu- 
trefaction, by absorbing water from 
the flesh (1127). It is also used as a 
source of sodium in the manufacture 
of caustic soda, and as a source of 

chlorine in the production of chlorohydric acid. It fuses at a red 
heat, and is hence used for glazing stoneware, earthenware, &c. 



Fig. 248. 



Fig. 249. 



Fig. 250. 



Fig. 251. 



Fig. 252. 




Crystallization of Common Salt. 



What is said of the natural occurrence and abundance of common salt ? 731. "What 
of its presence in plants and animals ? 732. State its properties. Mode of crystal- 



SODIUM AND ITS COMPOUNDS. 283 

734. Iodide and Bromide of Sodium, $TaI, NaBr. — These com- 
pounds are formed in sea water, and are interesting only as being 
the commercial sources of iodine and bromine. 

735. Carbonate of Soda, XaO, C0 2 + 10HO— Soda is supposed 
to fill the place in marine plants that potash does in land plants, 
and its carbonate was formerly obtained by leaching their ashes. 
It is now manufactured almost entirely from common salt by Le- 
blanc's process. This consists first in treating chloride of sodium 
with sulphuric acid, forming sulphate of soda, or salt caJce, and 
chlorohydric acid. The next step in the process is the substitu- 
tion of carbonic acid for the sulphuric acid in combination with 
the soda. This is effected by heating the salt cake with finely 
ground coal and chalk in a reverberatory furnace constructed for 
the purpose. After the mass is thoroughly fused, it is raked out 
into wooden troughs and allowed to cool, forming ball soda, or 
black ash. 

736. In this operation the carbon unites with the oxygen of the 
sulphate of soda, thus forming carbonic oxide which escapes, 
leaving sulphide of sodium. An interchange now takes place be- 
tween the carbonate of lime and the sulphide of sodium, carbo- 
nate of soda and sulphide of calcium being the result. In sym- 
bols, 

JSTaO, S0 3 + CaO, C0 2 + 4C = KaO, C0 2 + CaS + 4CO. 

The carbonate of soda, being the only constituent of the black ash 
that is readily soluble, is separated by leaching with warm water ; 
and lastly, the solution is evaporated to dryness, yielding the soda 
ash, or crude carbonate of commerce. Carbonate of soda is ex- 
tensively used in the manufacture of soap and glass, being both 
cheaper and purer than the ordinary potash. It is also used as a 
detergent, both in calico printing and in the laundry. 

737. Bicarbonate of Soda, ^aO, 2C0 2 , HO.— This is produced 
by passing carbonic acid through a solution of the carbonate. It 
forms the effervescing soda powders, and is used in bread making. 

738. Sulphate of Soda, EaO,SO 3 + 10HO {Glauber's salt).— 
This well-known salt may be formed by adding sulphuric acid to 
soda, and is chiefly procured in the manufacture of chlorohydric 

lization. 733. What are its uses? 734. What is said of iodide and bromide of 
sodium ? 735. How was carbonate of soda formerly obtained ? How at present ? 
736. Explain the changes. Uses of the salt. 737. What is bicarbonate of soda ? 



284 INORGANIC CHEMISTRY. 

acid. It has a bitter saline taste, and loses its water of crystalliza- 
tion on exposure to the air. 

739. Nitrate of Soda, ]STaO,¥0 5 (Soda- Saltpetre, Cubic Nitre). 
— Procured native from parts of Brazil and Chili. Attempts have 
been made to substitute this salt for nitrate of potash in the man- 
ufacture of gunpowder, but its tendency to attract moisture from 
the air has rendered it impracticable. Nitric acid is obtained from 
it, and it has been somewhat used as a fertilizer. 

740. Biborate of Soda, NaO, 2BO 3 + 10HO {Borax).— This is 
obtained from the evaporation of the waters of several lakes in 
Thibet. It is procured artificially by heating boracic acid with car- 
bonate of soda, the carbonic acid being expelled, and the boracic 
acid taking its place. This salt has an alkaline taste and reaction, 
and possesses the property of dissolving many metallic oxides ; 
hence, its use as a flux in the welding of metals. It dissolves off 
the coating of oxide formed when they are heated, thus presenting 
a clean surface. 

3. MANUFACTURE OP GLASS. 

741. "When pure sand is heated with potash or soda, they 
fuse into a viscous, transparent mass before passing into the form 
of a liquid. While in this state they may be moulded into any 
desired shape, retaining their form and transparency when cold. 
"When the alkaline earths are heated with them, they are brought 
into the same condition. Thus we have a compound easily 
moulded at a certain stage of fusion, uncrystalline when cold, 
but transparent, hard, strong, insoluble and durable — that is, com- 
mon glass. 

742. Materials of the Manufacture. — These are, first, silica, in 
the shape of pulverized quartz or sand. For the manufacture of 
the finest varieties of glass a pure white sand free from oxide of 
iron is employed. Second, there are the basic constituents of 
potash, soda, lime, magnesia, and oxide of lead, more or less pure, 
according to the quality of the glass required. Metallic oxides 
are employed as coloring agents. 



738. "What is sulphate of soda? 739. Nitrate of soda? 740. Give the composition 
of biborate of soda. Its uses. 741. When silica is heated with potash or soda, 
what results ? When with alkaline earths ? What are the properties of the com- 
pound? 742. What is the composition of glass? 743. Describe the process. How 



SODIUM AND ITS COMPOUNDS. 



285 



Fig. 253. 




Fig. 254. 



743. Process. — These materials are placed in pots or crucibles 
of refractory fire-clay, and several of them set in a large conical 
fiirnace. The fire is kept up day and 
night for months, the materials being 
added and withdrawn at pleasure. 
The plastic nature of the half-fused 
product adapts it for being easily 
worked into all desirable forms. The 

. ,. . , „ Rolling Melted Glass. 

workman dips an iron tube four or 

five feet in length into the waxy material, a portion of which ad- 
heres to it. To give it regular shape, he rolls it upon an 
even surface, Fig. 253 ; and to make it hollow, he blows 
through the tube. The glass may be pressed into various 
shapes between two moulds, one of which shuts into the 
other. Or it may be worked into globes and cylinders. 
If common window glass is to be made, the rounded mass 
upon the tube is blown into a pear shape, Fig. 254, which 
becomes elongated by swinging backward and forward, 
like a pendulum. By reheating, blowing and rolling, it is Biowrn^ 
worked into the form of a cylinder, Fig. 255, which is cut Glass * 
off at a and 5, and split along the line e. After again softening 
in the furnace, the cylinder is opened and spread out 
into a flat plate, as shown in Fig. 256. 

744. Colored Glass. — The coloring of glass is effect- 
ed by fusing into the materials a small quantity of me- 
tallic oxide. Oxide of copper gives a green tinge; 
oxide of gold a ruby color ; oxide of uranium a yel- 
low ; oxide of cobalt a deep blue ; oxide of manganese 
a purple ; while a mixture of the oxides of cobalt and 
manganese produces a black glass. Enamel watch- 
dials and semi-opaque transparencies are glass rendered 
milk white by oxide of tin, or bone earth. 

745. Varieties of Glass. — The silicates of lime, 
magnesia, iron, soda, and potash, in their impure form, produce the 
coarser kinds of glass of which green bottles are made. The sili- 
cates of soda and lime give the common window glass and French 
plate. Lime hardens glass, and adds to its lustre ; soda tends to 



Fig. 255. 




Glass Cylin- 
der. 



are the various forms obtained ? 744. How are the different colors produced ? 745. 
Of what does bottle glass consist ? Window glass ? What is the effect of lime ? 



286 



INORGANIC CHEMISTRY. 



Fig. 256. 




give it a greenish tinge. Bohemian glass, the most beautiful va- 
riety, hard and highly infusible, is a silicate of potash and lime. 

746. Imitation of Precious Gems. — Crystal glass, or flint 
glass, so called because pulverized flints were formerly used in 

making it, is a 
compound of the 
silicate of pot- 
ash and lead. 
The oxide of 
lead renders it 
very soft so as 
to be easily 
scratched, but 

Forming a Flat Sheet of Window Glass. greatly reduces 

its transparency, brilliancy, and refractive power. Sometimes 
the proportion of oxide of lead rises as high as 53 per cent. 
Glass of this composition forms what is called paste, and, when 
suitably cut, is used to imitate the diamond. By the addition 
of a trace of oxide of iron the yellow of the topaz is imitated, 
and by oxide of cobalt the brilliant blue of the sapphire is pro- 
duced. 

747. Annealing Glass. — If glass is suddenly cooled after fusion, 
there seems an unequal strain upon its particles, and it is brittle 
and liable to crack on the slightest scratch or jar. This is shown 
by ' Prince Kupert's drops, 7 little pear-shaped bodies, Fig. 257, made 

by dropping globules of melted glass into water. The 
cooling of the outer particles while the inner ones are 
still fluid, prevents the latter from expanding as they 
cool, thus causing such an enormous strain upon the 
surface, that if the small end be nipped off, the whole 
mass flies to pieces with an explosion. To obviate this 
difficulty, glass, after having received the desired 
form, is placed in large furnaces, which are maintained 
at a gradually decreasing heat for several days, until quite cool. 
This process is called annealing. Glass is cut by the diamond, and 
holes may be bored through it with the end of a three-cornered 
filfe, if the point of friction be kept wet with spirits of turpentine. 



Fig. 257. 




Rupert's 
Drops. 



746. What is flint glass ? What is the effect of lead upon it ? What is paste ? 747. 
Why must glass he annealed ? How is it done? How is glass cut and hored? 748. 



THE NEW METALS. 287 

4. CAESIUM, RUBIDIUM, LITHIUM, AMMONIUM 
CAESIUM. 

Sym. Ce. Equiv. 123.4. 

748. The extraordinary circumstances under which this metal 
and rubidium were discovered have been already stated (366). By 
evaporating a large quantity of the water containing caesium, 
Bunsex obtained a small amount of it as a chloride, and after- 
ward as an amalgam, with mercury. Such is its affinity for 
oxygen, that even in the state of alloy it oxidizes in the air and 
decomposes cold water. It is the most electro-positive element 
known, surpassing potassium, which formerly ranked first in this 
respect. It forms extremely caustic hydrates and carbonates, 
while its bicarbonate occurs iu permanent, glassy crystals. 

RUBIDIUM. 

Sym, Eb. Equiv. 85.36. 

749. This new metal has analogous properties with the pre- 
ceding. It is silver- white in color, with a crystalline structure, 
and forms compounds similar to those of caesium. Geandeatj has 
lately detected rubidium in the ashes of beets, tobacco, tea, and 
coffee. These metals are found associated with potassium, which 
they closely resemble, and are obtained in considerable quantity 
from the mineral Lepidolite. 

LITHIUM. 

Sym. L. Equiv. 7. Sp. Gr. 0.5936. 

750. This metal resembles potassium and sodium, though 
somewhat harder and considerably lighter, being the lightest 
metal known. Until recently, it was supposed to be very rare, 
but the late researches of Btjxsen and Kiechoff show that it is 
quite abundant and widely distributed. By the spectrum analysis 
they have found it in sea-water, in the water of springs, in the 
ashes of plants, and in the human blood. * 
— • 

What are the properties of caesium? 749. What of rubidium? Whence is it 
obtained ? 750. What are the properties of lithium ? Is it abundant ? 751. Why 
is ammonium beUeved to exist? What is its theory? 752. What are the 



288 INORGANIC CHEMISTEY. 

AMMONIUM. 

Sym. H 4 K Uquiv. 18. 

751. This is believed to be a compound radicle, having the 
nature of a metal, and forming oxides, salts, and even an amal- 
gam. Thus hydrated ammonia, H 3 N,HO, is regarded as an oxide 
of ammonium, H 4 N,0. It has never been separated. But if an 
amalgam of potassium and mercury be placed in a solution of sal 
ammoniac (752), it swells up, assumes a pasty consistence, but pre- 
serves its metallic lustre and the character of an amalgam. It is held 
that the potassium of the first amalgam has been replaced by am- 
monium, which has analogous metallic properties. The new amal- 
gam rapidly decomposes into mercury, ammonia, and hydrogen. 

752. Chloride of Ammonium, H 4 N, 01 (Sal Ammoniac). — A 
solution of ammonia is neutralized by chlorohydric acid, crystals of 
chloride of ammonium being produced, which have a sharp taste, 
and dissolve in thrice their weight of cold water. Sal ammoniac 
is chiefly obtained by neutralizing the ammoniacal liquor of the 
gas works by chlorohydric acid. On evaporating the liquor the 
salt appears in the form of the tough, fibrous crystals of commerce. 
It is volatilized by heat. It is used in soldering to cleanse mo- 
tallic surfaces, the chlorohydric acid dissolving the coat of oxide. 
Mixed with lime, which decomposes it and expels the ammonia, it 
is used to fill smelling bottles. 

753. Carbonate of Oxide of Ammonium (Carbonate of Ammo- 
nia). — There are several of these salts. Pure ammonia and car- 
bonic anhydride unite to form a neutral, anhydrous carbonate, 
H 3 N", C0 2 , pungent, volatile and very soluble in water. The com- 
mon sal volatile, or smelling salts of the shops, is a sesquicarbonate 
2H 4 N0, 300 2 . 

754. Sulphate of Oxide of Ammonium, H 4 NO, S0 3 HO, is 
prepared in a large way by neutralizing the ammoniacal liquor of 
the gas works with sulphuric acid. It is a valuable fertilizer. 
Mtrate of oxide of ammonium H 4 N0, ~R0 5 , HO, is a soluble salt 
used as a source of nitrous oxide. There is a host of compounds 
of a'mmonia which are of interest only to the professed chemist. 
The ammoniacal salts are all soluble, and yield the ammoniacal 

gpdor by adding caustic lime or potash, or at a high heat. 

properties of chloride of ammonium ? Its uses ? 753. What carbonates 
are mentioned ? 754. What other salts of ammonia ? 755. What is barium ? 



METALS OF THE ALKALINE EARTHS. 289 

§ II. Metals of the Alkaline Earths. 

BARIUM. 

Sym. Ba. Equiv. 68.6. 

755. Barium occurs in large quantity in the mineral known 
as heavy spar (sulphate of baryta). It is a white, silver-like 
metal, and has a strong affinity for oxygen, tarnishing on exposure 
to the air. 

756. Oside of Barium, BaO (Baryta), is a gray powder having 
a strong attraction for water, which it absorbs on exposure to the 
air, forming hydrate of baryta. The hydrate has an alkaline re- 
action, and unites with acids to form salts. 

757. Chloride of Barium, BaCl-f 2H0.— This salt is readily 
soluble in water. It is interesting only as being the usual test for 
sulphuric acid, with which it gives a dense white, insoluble precipi- 
tate of sulphate of baryta. 

758. Sulphate of Baryta, BaO, S0 3 (Heavy Spar).— This min- 
eral occurs in large quantities, and when ground is extensively 
consumed under the name of barytes in the adulteration of paints. 
Carbonate of baryta, BaO, 00 2 , is always formed when caustic 
baryta is exposed to the air. It occurs native in abundance, and is 
the chief source of the compounds of baryta. All the soluble salts 
of baryta act as powerful poisons when taken into the system. 

STRONTIUM. 
Sym. Sr. Equiv. 43.8. 

759. This metal resembles barium, in both appearance and 
properties. The nitrate of strontia is used considerably in the 
preparation of fire works, to the flames of which it imparts a 
beautiful crimson color. 

CALCIUM. 

Sym. Ca. Equiv. 20. Sp. Gr. 1.57. 

760. Calcium is a light yellow metal, somewhat harder than 
lead, very malleable, melts at a red heat, and oxidizes in the air. 
It exists in abundance in limestone, fluor spar, and gypsum. 

f 756. Oxide of barium ? 757. State the properties of chloride of barium ? Its use? 
758. What is said of sulphate of baryta? "What of carbonate? 759. Mention the 
uses of strontium ? 760. What is calcium ? Where is it found ? 761. What is the 
13 



290 INORGANIC CHEMISTRY. 

761. Oside of Calcium, CaO {Lime). — Calcium forms but one 
oxide, the well-known substance lime, which exists in such vast 
quantities in combination with carbonic acid as limestone, and 
with sulphuric acid as gypsum. Lime is prepared by burning lime- 
stone i» large masses in kilns. The carbonic acid is driven off into 
the air by the heat, and a white, stony substance remains, called 
quick lime, or caustic lime. One ton of good limestone yields 
11 cwt. of lime. When this is exposed to the air it first rapidly 
imbibes moisture and crumbles to powder. This gradually absorbs 
carbonic acid, and becoming less and less caustic, regains the neu- 
tral condition of the carbonate. 

762. Properties. — Lime exhibits the properties of a strong 
alkali, decomposing organic tissues and saturating the strongest 
acids. It is more soluble in cold than in hot water. Hence, when 
a cold saturated solution of lime-water is boiled, a portion of the 
lime is deposited, which accounts for the crust or fur which lines 
the interior of tea-kettles in localities where the water is impreg- 
nated with lime. 

763. Lime exists extensively in organized structures. The 
mineral portion of the skeleton of the higher animals consists of 
lime combined with phosphoric acid, and it is contained in the 
shells of the lower animals, chiefly united with carbonic acid. It 
also forms a large ingredient of plants. Lime is to be found in 
most fertile soils, and is much used in agriculture, as it promotes 
the decomposition of organic and inorganic matter, thus fitting it 
for assimilation by plants. 

764. Hydrate of Lime. — When water is poured upon quick- 
lime it absorbs it (every 28 lbs. of lime taking nine pounds of 
water), swells to thrice its original bulk, crumbles to a fine white 
powder, and is converted into a hydrate of lime, CaO, HO. This 
process is called slaking, and sufficient heat is often produced by 
the chemical action to ignite wood. Lime water is a saturated, 
transparent solution of lime in water. Cream or milk of lime is a 
thick mixture of the hydrate with water, such as is used in white- 
washing. In tanneries the hides are immersed in milk of lime, 

pomposition of lime ? How is it obtained ? What is the effect of exposure to the 
air? 762 State the properties of lime. Explain the cause of the crust of tea- 
kettles. 163. Where is lime found in organic structures? What are its uses in 
agriculture? 764. How is the- hydrate obtained? What is lime water? M ; lk of 
lime ? Its uses ? 765. Of what is the best mortar made ? What is the effect of 



METALS OF THE ALKALINE EARTHS. 291 

which partially decomposes them, so that the hair may be easily 
removed. 

765. Mortar and Cement. — Lime, mixed with sand, forms the 
mortar employed by builders to cement stones and bricks. To 
make the best mortar, the lime should be perfectly caustic and 
the sand sharp and coarse-grained. The nature of the changes by 
which the mortar becomes hardened is not satisfactorily explained. 
It is supposed to be owing in part to the lime absorbing carbonic 
acid from the air, and hardening into a carbonate of lime. In 
time the lime also partially combines with the silica of the sand? 
forming an exceedingly hard silicate of lime. Common mortar, 
when laid in water, not only refuses to harden, but its lime grad- 
ually becomes dissolved out and washed away. Hydraulic cement 
possesses the property of solidifying under water. This quality is 
owing to the presence of clay (silicate of alumina) in the lime of 
which it is composed. 

766. Carbonate of Lime, CaO, C0 2 . — Vast deposits of this 
salt are distributed all over the globe in the form of limestones, 
marbles, chalks, marls, coral-reefs, shells, &c. Numerous and ex- 
tensive as are these deposits, it is conjectured that they are all 
of animal origin. The densest limestone and the softest chalk are 
found to consist of the aggregated skeletons, or shells of myriads 
of tribes of the lower animals, which have existed in some former 
period of the world's history. The formation of coral reefs, which 
are sea-islands of carbonate of lime built up from the depths of the 
ocean by minute aquatic animals, is an example of similar deposits 
now in process of formation. 

767. Carbonate of lime is decomposed by heat into carbonic 
acid and lime. It is soluble in water containing free carbonic 
acid ; hence the well and spring water of lime districts becomes 
impregnated with it, hard water being the result. When the 
hardness of water is due to this cause, it may be softened by the 
addition of lime water, which neutralizes the excess of carbonic 
acid, the carbonate being precipitated. Water containing car- 
bonate of lime in solution deposits a portion of it on free expo- 
sure to the air. Examples of this are often seen in caves. The 
water, as it trickles from fissures in the roof, deposits its carbonate 

time upon it? What is hydraulic cement ? 766. What forms of carbonate of lime 
exist naturally? What is the origin of these deposits? What of coral-reefs? 
767. What is the effect of heat upon carbonate of lime ? How may hard water be 



292 



INORGANIC CHEMISTRY. 



Fig. 258. 



until pendent masses like those 
represented in Fig. 258 are 
formed. These are called sta- 
lactites, and where the water 
strikes on falling, other forms 
similar to those above grad- 
ually grow up from the floor, 
and are known as stalagmites. 
These often unite, thus form- 
ing a column. 

768. Sulphate of Lime, CaO, 

S0 3 + 2HO {Gypsum, Plaster, 

S^^^^^^^^^^ Alabaster). — This salt occurs 

in many parts of the world, 
forming extensive rocky beds. 
In its pure, transparenf form, 
it is known as selenite, and in its compact and earthy varieties as 
gypsum, plaster of Paris, and alabaster. "When powdered gypsum 
is heated to nearly 300°, it parts with its water of crystallization. 
If now it is made into a liquid paste with water, it again combines 
with it, and speedily hardens or sets, resuming its stony aspect. 
Owing to this property, it is used to take impressions of objects 
and make casts, by being run into hollow moulds. Colored and 
mixed with glue, it is used for the ornamental designs in architec- 
ture called stucco-work. Gypsum is used extensively as a fertilizer. 




Effects of lime in caves. 



Jr 



MAGNESIUM. 
Sym. Mg. Equiv. 12. 8p. Gr. 1.7. 



769. This is a white, brilliant, malleable metal, found abun- 
dantly in combination in many rocks and minerals, and occurs 
also in sea- water as a chloride. 

770. Oxide of Magnesium, MgO (Magnesia). — Only one 
oxide of magnesium is known, and this is found by igniting the 
carbonate. It is a white, light powder, with feeble alkaline prop- 
erties, very sparingly soluble in water, but dissolving readily in 
acids. It is found in some minerals, in mineral waters, and in the 

softened? What are stalactites? Stalagmites? 768. Give composition of sulphate 
of lime. How does it occur? What is selenite? Use of gypsum for making 
casts? What are its other uses? 769. Pescribe magnesium. 770. State the 



ALUMINUM AND ITS COMPOUNDS. 



293 



ash of nearly all plants. In medicine it is used as a mild aperient 
and antacid. 

771. Sulphate of Magnesia, MgO, S0 3 + 7HO {Epsom Salts).— 
This is a common ingredient of mineral waters, and takes its name 
from the circumstance of its being contained in great quantities 
in the springs near Epsom, in England. The commercial supply- 
is chiefly derived from sea-water, by precipitating the magnesia 
with lime, and then adding sulphuric acid. It may also be ob- 
tained from magnesian limestone. It is soluble in water, has a 
bitter, saline taste, and is used in medicine as a cathartic and an 
antidote to various poisons. It has also been used as a fertilizer. 



CHAPTEE XV. 



METALS WHICH DECOMPOSE WATER AT A RED HEAT. 



Aluminum, 


Ceeium, 




Glucinum, 


Ieon, 


The first ten metals 


Thoeinum, 


Manganese, 


of this group are metals 


Ytteium, 


Nickel, 


of the earths, but with 


Eebium, 


Cobalt, 


the exception of alu- 


Teebittm, 


Zinc, 


minum, they are very 


ZlECONIUM, 


Cadmium, 


rare, and of no special 


Lanthanum, 


Tin. 


interest. 


Didtmium, 






§ 1. Aluminum and its Compounds. 




aluminum. 


Sym. 


Al. Equiv. 13.7 


. Sp. Gr. 2.5. 



772. This important metal was discovered by the German 
chemist, AYohlek, in 1827. It is found in nature in immense 
quantities, being the metallic base of alumina which forms the 
argillaceous rocks, beds of clay, and a large proportion of granite. 
It is a shining, white metal, of a shade between silver and pla- 



properties of magnesia. "Where is it found ? Its uses ? 771. What is sulphate of 
magnesia? What are its properties? Its uses? 772. Discovery of aluminum. 



294 INORGANIC CHEMISTRY. 

tinum, harder than zinc, lighter than glass, and of remarkable 
strength and stiffness. It resists the oxidizing influence of moist 
air like silver, melts at a still lower temperature than that metal, 
and, pound for pound, occupies four times its space. It is more 
sonorous than any other metal, giving forth a clear musical sound 
when struck. It is malleable and ductile like iron, exceeds it in 
tenacity, and combines with carbon, forming a cast metal which 
is not malleable. It resists the action of cold nitric and sulphuric 
acids, and, unlike silver, is not tarnished by sulphuretted hydrogen. 
It dissolves chlorohydric acid, forming a chloride, and conducts 
electricity nearly as well as silver. Aluminum is obtained by de- 
composing chloride of aluminum by means of sodium, and as sodium 
is at present expensive, the manufacture of aluminum renders it 
a costly metal ($4 per lb.). It will undoubtedly be greatly cheap- 
ened, when it will become of invaluable service in the 'arts. Its 
alloys will be noticed in Chap. XVII. 

773. Sesquioxide of Aluminum, A1 2 3 , {Alumina). — This, 
which is the only oxide of alumina, is an abundant natural product, 
being found in all soils and rocks. Crystallized and colored by 
oxide of chromium, it forms the ruby and sapphire, which rank 
next to the diamond in hardness and value. In a more massive 
form it is known as corundum or emery. Alumina seems to possess 
the properties of both an acid and a base, uniting with either to 
form definite salts. It has a powerful attraction both for vegetable 
coloring matter and for the fibre of cloth ; hence, it is used by dyers 
to ^x the colors upon their fabrics. It is then said to act as a 
mordant. Alumina is precipitated from organic solution by an 
alkali, and, if there is any vegetable or animal coloring matter 
present, this is also carried down with the alumina, forming what 
is termed a lake. Carmine is a lake of cochineal. Alumina also 
absorbs and combines with oily matters ; hence, a certain kind of 
clay, called fullers* earth, is used to extract grease from wood, 
paper, &c. 

774. Sulphate of Alumina and Potash, KO, S0 8 + AL0 3 , 3S0 3 

+ 24HO (Alum). — Small quantities of this important salt are found 

native, but for commercial purposes it is prepared artificially by 

Where does it occur ? What are its properties ? How is it obtained ? Its price ? 
773. What is alumina? Mention some of its varieties. Its properties. How is 
it used by dyers ? How is carmine formed ? What is fullers' earth ? 774. Give 
the composition of alum. How is it formed ? 775. Its properties ? What is burnt 



ALUMINUM AND ITS COMPOUNDS. 295 

several different methods. In this country it is formed by treat- 
ing alumina or clay with sulphuric acid, and, after the lapse of a 
few months, adding potash, either in the form of sulphate or car- 
bonate. The whole is then leached, and the alum separated from 
the solution by crystallization. 

775. Alum has a sweetish, styptic taste, and is soluble in 18 
parts of cold water, or in its own weight of boiling water, the solu- 
tion having an acid reaction. When heated, alum swells up into 
a light, puffy condition, at the same time giving off its water of 
crystallization, and leaving a white, anhydrous, infusible mass 
known as burnt alum. 

776. Alum is used largely for purifying and preserving skins, 
for mordants in dyeing and calico printing, for glazing paper, for 
hardening and whitening tallow, clarifying liquors, and in medi- 
cine as an astringent and caustic. Wood impregnated with it is 
almost incombustible. 

777. Sulphate of soda or ammonia may replace the sulphate of 
potash in combination with the alumina, thus giving a soda or am- 
monia alum. In like manner the sesquioxides of iron, manganese*, 
chromium, &c, being isomorphous with alumina, may replace it, 
forming an iron, manganese or chrome alum, all of which have the 
same crystalline form. 

778. Silicate of Alumina, or Clay, is the result of the decom- 
position of feldspathic and silicious rocks, and is the basis of all 
kinds of pottery. Its adaptation for this purpose depends upon its 
plasticity when mixed with water, the readiness with which it 
may be moulded, and also upon its capability of solidifying when 
exposed to a high heat. After burning, the ware, though hard, is 
porous, and absorbs water with avidity, even allowing it to filter 
through. To prevent this, the ware is covered with a glassy coat- 
ing, or glazed. 

779. Porcelain consists of a mixture of decomposed feldspar 
(called kaolin), silica, and a small proportion of lime, the ingre- 
dients being carefully selected, and thoroughly ground and incor- 
porated. When moulded into the proper form, the articles are 
dried and subjected to a high heat in a furnace, in which state the 

alum? 776. Uses of alum? 777. How does it illustrate isomorphism? 778. Give 
the composition and origin of clay. "What quality adapts it for pottery. Why 
must the ware be glazed ? 779. What is porcelain ? Describe its manufacture. 
How is it colored ? 780. How is common red pottery ware made ? Why is it ob- 



296 INORGANIC CHEMISTRY. 

ware is called biscuit. They are then glazed by dipping them into a 
solution of powdered quartz and feldspar, which, when heated, fuses 
into the ware, giving it a vitreous coating which adds to its com- 
pactness and strength. The partial fusion of the materials gives 
porcelain the beautiful semi-transparency which distinguishes it 
from earthen ware. In coloring porcelain, the patterns are print- 
ed on paper which is applied to the biscuit while the color is still 
moist. When the color is absorbed, the porcelain is subjected to 
another baking, which fixes the tint. In the finer kinds of porce- 
lain the colors are mixed with a fusible glaze, and applied with a 
hair pencil. 

780. Common Red Pottery Ware owes its color to oxide of 
iron, and is glazed with a preparation of clay and oxide of lead. 
Vessels thus coated are objectionable for domestic use, as the lead 
glaze is sometimes dissolved by acids, producing poisonous effects. 
Bricks are unglazed. Stone ware is a coarse kind of porcelain 
glazed with salt. Fire bricks, muffies, and Hessian crucibles are 
made of a pure, infusible clay, containing a large amount of silica. 
The beautiful ljlue pigment ultramarine is a silicate of alumina, 
supposed to be colored with hyposulphite of soda and sulphide of 
sodium. 

§ II. Iron and its Compounds. 

IRON. 

Sym. Fe. (Ferrum.) Equiv. 28. Sp. Gr. 7.8. 

781. Were we to seek for that circumstance which might best 
illustrate the peculiarities of ancient and modern civilization, we 
should perhaps find it in the history of this metal. The ancients, 
imbued with a martial spirit and passion for conquest, made iron 
the symbol of war, and gave it the emblem of Mars. And if it 
were required also to symbolize the pacific tendencies of modern 
society, its triumphs of industry and victories of mind over matter, 
its artistic achievements and scientific discoveries, we should nat- 
urally employ the same metal iron. As gold and jewels have long 
been the type of barbaric and empty pomp, so iron may now be 
well regarded as the emblem of beneficent and intelligent industry. 

jectionable for domestic purposes? What is stoneware? Firebrick? "What 
ultramarine ? 781. What is said of the relations of iron to civilization ? 782. Men- 



IKON AND ITS COMPOUNDS. 297 

782. Uses of Iron. — Iron in some of its innumerable forms 
ministers to the benefit of all. The implements of the miner, the 
farmer, the carpenter, the mason, the smith, the shipwright, are 
made of iron and with iron. Roads of iron, travelled by iron steeds, 
which drag whole townships after them and outstrip the birds, 
have become our commonest highways. Ponderous iron ships are 
afloat upon the ocean, with massive iron engines to propel them ; 
iron anchors to stay them in storms ; iron needles to guide them, 
and springs of iron in chronometers by which they measure the 
time. Ink, pens, and printing presses by which knowledge is 
scattered over the world, are alike made of iron. It warms us in 
our apartments ; relieves our jolts in the carriage ; ministers to our 
ailments in the chalybeate waters or the medicinal dose ; it gives 
variety of color to rocks and soils of the earth, nourishment to 
vegetation, and vigor to the blood of man. Such are the powers 
of a substance which chemists extract from an otherwise worth- 
less stone. 

783. Iron occurs in nature almost universally in a state of 
combination. The mineral masses which it forms with oxygen, 
carbon, sulphur, and the metals, and from which it is extracted, 
are called its ores. Of these there are no less than 19 varieties, 
8 or 9 of which are worked for their iron alone, while several of 
the others yield substances of great value in the arts, such as sul- 
phur, arsenic, chronium, &c. 

784. Ores of Iron. Magnetic iron ore, FeO,Fe 2 3 (Loadstone). 
— This is a combination of the protoxide and sesquioxide, and is one 
of the richest ores of iron, containing 72 per cent, of the metal 
and 28 of oxygen. It is strongly magnetic, of a grayish color, and 
when rubbed gives a black powder. This ore is very widely dif- 
fused, and furnishes iron of the best quality. It affords the supe- 
rior iron obtained from Eussia, Germany, and Sweden. 

785. Specular, or Red Iron Ore is a sesquioxide, Fe 2 3 , very 
hard and sometimes presenting the appearance of polished steel. 
"When coarse, it is of a brown color, but its powder is always red, 
a quality which distinguishes it from the magnetic oxide. This 
oxide contains 63 per cent, of iron to 37 of oxygen. It exists in 

f tion some of the uses of iron. 783. How does it occur ? What is said of its ores ? 

784. What is the composition of magnetic ore ? What its quality ? Its properties ? 

785. What is specular iron ore ? How distinguished from the magnetic ? When 
are red clays called ores? 786. What is red hematite? Brown hematite? 

I • 13* 



298 INORGANIC CHEMISTRY. 

all the red clays, which, when they yield 25 per cent, of the metal, 
are termed ores. 

786. Red Hematite, Fe 3 , is another anhydrous sesqnioxide, 
found in large quantities and considerably worked. Brown Hema- 
tite, or hydrated peroxide of iron, 2Fe 2 3 3HO, is very abundant 
throughout the world and particularly in the United States. It 
affords a yellow powder, and is not attracted by the magnet. It 
contains about 86 per cent, of peroxide of iron to 17 per cent, of 
water. 

787. Carbonate of Iron (Spathic Iron, Steel Ore).— This con- 
tains 63 per cent, of oxide of iron, 34 per cent, of carbonic acid, and 
a small quantity of lime, magnesia, and manganese. A variety of 
steel is made directly from this ore. It is the source of the cheap 
German steel. 

788. Clay Ironstone is another carbonate of iron, having a 
yellowish-brown color, and is one of the chief sources of the iron 
of commerce. It occurs among the coal measures mixed with 
clay, and contains about 37 per cent, of iron. There are several 
other ores worked for their iron to some extent, but those men- 
tioned are the most important. 

789. Bisulphide of Iron, FeS 2 , is the pyrites of mineralogists, 
so named because it was used in firelocks to strike fire with steel 
before the introduction of gun flints. It occurs in large quantities 
and under several different forms. Yellow pyrites, when in the 
form of minute brilliant scales, is sometimes mistaken for gold 
(fooVs gold). It is tested at once by the sulphurous odor it emits 
when heated. This variety contains 47 per cent, of iron to 53 of 
sulphur. Pyrites is chiefly prized as a source of copperas, alum, 
Spanish brown, sulphur, and sulphuric acid. It is never worked 
for its iron. 

790. Obtaining the Metal.— The process of separating iron 
from its ores is called reducing or reviving it, and the ores are said 
to be smelted. The operation is conducted in tall chimney-like 
structures, termed blast furnaces. They are constructed of stone, 
and lined with the most refractory fire brick, having the form 
seen in Fig. 259. The top or mouth of the furnace serves for 
charging it, and for the escape of smoke ; it is both door and 

787. What is the composition of steel ore? 788. Of clay iron stone? What other 
ores are mentioned ? 789. What is bisulphide of iron ? What is fool's gold ? Use 
of pyrites ? 790. How is the operation of smelting performed ? Describe the blast 



IRON AND ITS COMPOUNDS. 



299 



Fig. 259. 




chimney. The tubes or tuyere pipes at the bottom serve to sup- 
ply the air, which is forced in by means of immense blowing cyl- 
inders driven by water or steam 
power. The amount of air thus 
forced through some large furnaces, 
exceeds 12,000 cubic feet per minute. 
Formerly the air was used at the 
ordinary temperature {cold Mast), 
but within a few years an immense 
improvement has been effected by 
heating the air before it enters the 
furnace (hot Mast), 

791. In some cases the materials 
are drawn up an inclined plane to 
the mouth of the shaft by the same 
engine that impels the blast mechan- 
ism. The furnace is supplied with ^0=^ 
ore, coal, and limestone broken into k ■■■— -± - 4 p isl&- _._ jjjfc 

small fragments. "When the heat is ^—^"" : l ~ ' " xzr-4 

sufficiently intense the carbon of the 

fuel deoxidizes the iron, and carbonic acid is also expelled from 
the lime, leaving it caustic. Sand and clay, in greater or less 
quantities, now remain combined with the iron. The lime, acting 
as a flux, unites with these, forming the slag or scoria, a crude 
semi-vitreous product. The melted iron, falling to the bottom of 
the furnace, accumuates and is drawn off by taking out a tap or 
plug. It is allowed to run into a bed of 
sand, containing straight channels and fur- 
rows running at right angles. The former 
are called by the workmen the sow, and 
the latter the pigs; hence the term pig- 
iron. As the contents of the furnace are 
removed from below, crude ore is con- 
stantly supplied from above, and the opera- 
tion goes on day and night uninterruptedly 
for a course of years, or until the fabric demands repair. 

792. The product of the smelting furnace is cast iron. This 



Fig. 260. 




Texture of Cast Iron. 



furnace ? 791. What are the changes occurring in the furnace ? 792. What are the 
properties of cast iron ? To what due? What is wrought iron? 793. State the 



300 INOEGANIC CHEMISTRY. 

has a granular texture, Fig. 260, and is so brittle that it cannot be 
forged, but may be remelted and cast into moulds. It expands 
when first poured into the mould, so as to copy it perfectly, but 
subsequently contracts. The expansion is caused by the particles 
assuming a crystalline arrangement while consolidating ; the con- 
traction by the cooling of the metallic mass when solidified. These 
properties of brittleness and easy fusibility are due to the presence 
of a considerable quantity of carbon and other impurities, the 
removal of which converts it into wrought iron. 

793. Physical Properties of Iron. — Iron is of a grayish white 
color, and when polished has a perfect lustre. The various condi- 
tions under which it appears in the arts are due to the presence or 
absence of certain other substances, such as carbon, silicon, sul- 
phur, phosphorus, manganese, and arsenic. In the absence of 
these substances, iron is so malleable that books have been made 
of it with leaves as thin as paper, and so ductile that it may be 
drawn out into wires as thin as a hair. Its most useful quality, 
however, is its superior tenacity, or power of resisting strain ; no 
other metal being equal to it in this respect. Hence the value of 
iron in the manufacture of cannons and mortars, where the im- 
mense expansive force of gunpowder is to be resisted, and in the 
making of wire cables for suspension bridges. Bo great is its te- 
nacity that an iron wire 0.075 of an inch in diameter is capable of 
supporting a weight of 449 pounds. 

794. Passive Iron. — In its ordinary condition iron oxidizes 
rapidly in the air, and dissolves in nitric acid. But under several 
circumstances it assumes different and peculiar chemical relations. 
If momentarily immersed in a strong mixture of nitric and sul- 
phuric acids it retains its metallic lustre, but has lost the power 
of either being oxidized in the air or of dissolving in nitric acid ; 
it has become passive, or assumed an allotropic form. 

795. Wrought Iron. — The operation of separating carbon and 
other foreign substances from cast iron is usually conducted 
in reverberatory furnaces. In this process the fire is not 
mingled with the metal, as in the case of smelting, but the 
material is melted by causing the flame to impinge upon it 
on its way through the furnace, as shown in Fig. 261. A work- 
physical properties of iron. 794. What is passive iron ? 795. How is wrought 
iron obtained ? 796. How may the quality he still improved ? How is wrought 



IKON AND ITS COMPOUNDS. 



301 



Fig. 261. 




Puddling Furnace. 



man, with a long, oar-shaped implement of iron, stirs (puddles) 
the melted mass until the carbon and other impurities of a like 
nature are burned away, and the 
metal becomes thick and pasty. 
This is called puddling. The pud- 
dler then rolls up from the mass a 
ball of about 75 lbs. weight, which 
he transfers to the tilting or trip 
hammer, where it is beaten by 
heavy blows into a crude bar. By 
this operation the liquid impurities, 
consisting chiefly of silica and alu- 
mina, are squeezed out, as water is 
expelled from a compressed sponge. 

796. The metal," still hot, is then passed between grooved cyl- 
inders, where it is rolled out into oar iron. The quality of metal 
is greatly improved when these bars are broken up, bound together, 
reheated to the welding point, and again passed through the roll- 
ing mill. This latter operation is often repeated several times, 
and is known &s piling or fagoting. Wrought iron may be pro- 
duced directly from the magnetic ore. The process is conducted 
on what is termed a Catalan forge, or oloomary, a structure much 
resembling a blacksmith's forge, on a large scale. The operation 
consists in the reduction of the oxide by means of charcoal, after 
which the iron obtained is put through the same course of ham- 
mering and rolling as if it came from the puddling furnace. 

797. "Wrought iron has a fibrous tex- 
ture, and rough, hackly fracture, Fig. 262. 
It is said to lose this tough, fibrous charac- 
ter by the effect of constant jarring, and 
to become crystalline. It usually contains 
a small quantity of carbon, which hardens 
the iron without affecting its other prop- 
erties, but if the amount exceeds \ per 
cent., it renders the iron cold-short, that is, 
brittle and liable to snap asunder when 
cold. The presence of sulphur, even in so 
small a proportion as T o,^o«n unfits the iron for being worked at a 



Fig. 262. 




Texture of Wrought Iron. 



iron made from the ore ? 797. What is the effect of carbon in wrought iron ? Of 
sulphur \ 798. What is welding ? What precaution is necessary ? What metals 



302 INORGANIC CHEMISTRY. 

red heat, as it is liable to split when hammered ; it is then said to 
be hot-short. 

798. Welding of Iron. — When wrought iron is heated to 
whiteness, it becomes soft, pasty, and adhesive, and two pieces in 
this condition may be incorporated, or hammered into one. This 
is called welding. Daring the heating a film of oxide is formed 
upon the surface of the metal, which would obstruct the ready 
cohesion of the separate masses. To prevent this, the smith 
sprinkles a little sand upon the hot iron, which combines with the 
oxide, forming a fusible silicate of iron, which is easily forced out 
by pressure, leaving clean surfaces that unite without difficulty. 
This important quality is possessed only by iron, platinum, and 
sodium. All the other metals pass suddenly from the solid to the 
liquid state at their respective melting points. 

799. Steel. — This remarkable modification of iron is a com- 
pound of the metal with about one and a half per cent, of carbon. 
It is made by imbedding bars of the best wrought iron in pow- 
dered charcoal, in boxes or sand- furnaces, which exclude the air, 
and heating it intensely for a week or ten days. The chemical 
changes are obscure ; probably carbonic oxide penetrates the 
heated metal, is decomposed, surrenders part of its carbon and 
escapes as carbonic acid. The steel when withdrawn has a pecu- 
liar rough, blistered appearance, and is hence known as blistered 
steel. This method of making steel is called the process of cemen- 
tation. 

800. In its properties steel combines the fusibility of cast iron 
with the malleability of bar iron. Its value for cutting instru- 
ments, springs, &c, depends upon its quality of being tempered. 
When heated to redness and suddenly quenched in cold water, it 
becomes so hard as to scratch glass. If again heated and cooled 
slowly, it becomes as soft as ordinary iron, and between these two 
conditions any required degree of hardness can be obtained. As 
the metal declines in temperature, the thin film of oxide upon its 
surface constantly changes its color. The workmen are guided by 
these tints. Thus a straw color indicates the degree of hardness 
for razors ; a deep blue for sword blades, saws and watch springs. 
Steel receives a higher polish than iron and has less tendency to 



possess this property ? 799. What is steel ? How is it made ? What is blistered 
steel ? 800. Upon what does its value for cutting instruments depend ? How is this 



IRON AND ITS COMPOUNDS. 303 

rust. Nitric acid placed upon steel corrodes it, and leaves the car- 
bon as a dark gray stain ; hence it is often used for writing and 
ornamental shading upon this metal. 

801. Oxides of Iron. — Iron has a strong affinity for oxygen, 
with which it forms four well marked compounds, viz. : the pro- 
toxide FeO; the sesquioxide ' or peroxide Fe 2 3 ; the magnetic 
oxide, supposed to be a combination of the two preceding, and 
having the formula FeO, Fe 2 5 , or Fe 3 4 , and ferric acid Fe0 3 . 
The first three are the most abundant, existing in stones, rocks, 

nd soils, and imparting to them their red and yellow colors. 

802. The Protoxide is not found in the separate state, as it 
rapidly absorbs oxygen, and passes into the sesquioxide. It is the 
basis of all the green salts of iron, and in a state of combination is 
widely diffused, existing chiefly in those rocks having a greenish 
or dark tint. The iron in chalybeate waters usually rises to the 
surface as a protoxide, and there absorbing oxygen from the air, 
the peroxide is formed, and sinks to the bottom as an insoluble, 
reddish sediment. 

803. The Anhydrous Sesquioxide is known in commerce 
under the name of colcatliar or rouge, and is extensively employed 
in polishing glass, jewelry, &c. It is also used as a pigment. The 
hydrated sesquioxide, associated with alumina, forms the umbers 
and ochres so much used as pigments. 

804. Magnetic Oxide. — The black scale, which forms on iron 
when heated, consists of magnetic oxide. This is also the result 
of the combustion of iron in oxygen gas. It is the only oxide pos- 
sessing magnetic properties. Ferric acid is a very unstable com- 
pound, and is of little account. 

805. Protosulphate of Iron {Green Vitriol, Copperas). — This 
salt, as its name indicates, is a compound of the protoxide of iron 
with sulphuric acid. It is largely manufactured at Stafford, Conn., 
from iron pyrites, which furnishes by oxidation both the acid and 
the base. It is used in dyeing, for making ink and Prussian blue, 
and in medicine. It often exists in soils to a pernicious extent, 
but is decomposed by lime ; gypsum being formed. 

determined ? What is the effect of nitric acid upon steel ? 801. "What is the compo- 
sition of the oxides of iron ? 802. G-ive an account of the protoxide. 803. Of the anhy- 
drous sesquioxide. Of the hydrated. 804. What is the magnetic oxide ? 805. What 



304 INORGA1S1C CHEMISTRY. 

§111. Manganese, JVicJcel, Zinc, Cobalt, Cadminm, Tin. 

MANGANESE. 

Sym. Mn. Equiv. 27 AS. Sp. Gr. 8. 

806. Manganese is a hard, brittle metal of a grayish-white 
color. It never occurs pure in nature, but its oxides are found 
combined with many ores of iron, a metal which it resembles in 
many of its properties. Manganese is obtained by making its 
oxide into a paste with oil and lampblack, and heating it to white- 
ness in a covered crucible. It rapidly oxidizes when exposed to 
the air, and is best preserved in naphtha. 

807. It forms no less than seven different compounds with 
oxygen. Its oxides are diffused in small quantities through most 
soils, and traces of them may be detected in the ashes of nearly 
all plants. Protoxide of manganese is of a pale green color and is 
a powerful base, giving rise to rose-colored salts. The peroxide 
or Hack oxide, Mn0 2 , is employed as a cheap method of procuring 
oxygen on a large scale, and for the manufacture of chlorine and 
steel. It is also used under the name of glassmaJcer's soap to de- 
stroy the green tinge given to glass by protoxide of iron and to 
oxidize carbonaceous impurities. If added to glass in large quan- 
tities, it gives it a purple color. 

NICKEL. 

Sym. M. Equiv. 29.5. Sp. Gr. 8.8. 

808. This is a brilliant white metal, somewhat malleable and 
ductile. At ordinary temperatures it is magnetic, but if heated 
above 630° it loses this property, acquiring it again, however, on 
cooling. It is used principally in the formation of alloys. Nickel 
forms oxides, but they are of little interest. 

COBALT. 

Sym. Co. Equiv. 29.5. Sp. Gr. 8.9. 

809. Cobalt generally occurs in combination with arsenic or 
nickel, though it is sometimes found native in meteoric masses. 

the protosulphate ? 806. "What is manganese ? How is it obtained ? How kept ? 
807. What is said of its compounds with oxygen ? What of the protoxide ? The 
peroxide? Its uses? 808. What are the properties of nickel? 809. What is 



IKON AND ITS COMPOUNDS. 305 

"When obtained pure it is a reddish- white, hard, brittle, strongly 
magnetic metal. It forms two oxides; the protoxide, CoO, and 
the sesquioxide, Co 2 3 . The protoxide is a grayish powder, 
which, when fused with glass, imparts to it a beautiful blue color. 
Smalt is a glass, colored blue by oxide of cobalt and then reduced 
to an impalpable powder. It is used for coloring on glass, paper, 
&c. Zaffire, used to impart a blue color to ordinary earthen ware, 
is an impure oxide of cobalt. 

810. Chloride of Cobalt forms a pink solution which turns 
blue when dried. This solution is used as a sympathetic ink, the 
characters written w r ith it being so pale as to be invisible till 
warmed, when they appear blue. On cooling they absorb moist- 
ure and again disappear. 

ZINC. 

Sym. Zn. Equw. 32.5. Sp. Gr. 7. 

811. Zinc is a brilliant, bluish-white metal, found abundantly 
in nature in combination with sulphur as zinc-blende, and with 
oxygen and carbonic acid as calamine. It also exists in great 
quantities as a red oxide in New Jersey. At common tempera- 
tures it is brittle, but when heated from 212° to 300° it may be 
rolled out into thin sheets, and retains its malleability when cold. 
At 400° it again becomes quite brittle ; at 770° it melts, and when 
exposed to air takes fire, burning with a whitish-green flame and 
forming oxide of zinc. Zinc soon tarnishes in a moist atmosphere, 
forming a thin film of oxide, which resists further change. This 
property renders it useful for a variety of purposes, such as for 
gas pipes, gutters, roofing, and for galvanizing iron, thus prevent- 
ing it from oxidation. It is also used in the preparation of hy- 
drogen gas. 

812. Oxide of Zinc, ZnO.— This is formed when zinc is burned 
with free access of air. It is a fine, white powder, and is the only 
oxide of zinc known. It is used largely as a paint. 

813. Sulphate of Zinc, ZnO,S0 3 {White Vitriol).— This may 
be prepared either by roasting the sulphide, or by the action of 
sulphuric acid on the pure metal. It strongly resembles the sul- 

cobalt? Mention its compounds. State their uses. 810. What is chloride of 
cobalt ? 811. What is zinc ? How does it occur ? State its properties. Its uses. 
812. What is oxide of zinc? For what used? 813. How is sulphate of zinc ob- 



306 INORGANIC CHEMISTRY. 

phate of magnesia, and is used in medicine and in certain opera- 
tions of calico printing. 

CADMIUM. 

Sym. Od. Equiv. 56. Sp. Gr. 8.6. 

814. Cadmium is usually found associated with zinc. It is a 
white, volatile metal, somewhat malleable and ductile, and so soft 
as to leave a mark when rubbed upon paper. It forms an oxide, 
CdO, which may be obtained by burning the metal in air. 

TIN. 
Sym. Sn. (Stannum). Equiv. 59. Sp. Gr. 7.8. 

815. Tin is a brilliant, silver- white metal, which occurs most 
abundantly in Cornwall, England. It has been found in this coun- 
try only at Jackson, N". H., and in small quantities. It is softer 
than gold, slightly ductile and very malleable, common tin foil 
being often not more than j-^-^ of an inch in thickness. It melts 
at 442°. The peculiar crackling sound given by tin when bent, is 
due to a disturbance of its crystalline structure. Owing to its 
weak affinity for oxygen it tarnishes but slightly on exposure to 
the air or moisture, and is therefore very valuable for domestic 
utensils. This property also renders it useful for coating other 
metals to prevent them from oxidizing. Sheet iron coated with 
tin, with which it forms an alloy, constitutes common tin ware. 

816. There are two well marked oxides of tin; the protoxide, 
SnO, and the binoxide, Sn0 2 . The protoxide acts as a base, but 
the binoxide, when combined with water, has distinct acid proper- 
ties. Tin forms several very important alloys. 



CHAPTEK XVI. 

METALS WHICH DO NOT DECOMPOSE WATER. 

chromium, • colttmbittm, gold, 

Arsenic, Tantalum, Platinum, 

Antimony, Molybdenum, Palladium, 

Bismuth, Tungsten, Ehodium, 

Copper, Vanadium, Euthenium, 

Lead, Uranium, Osmium, 

Thallium, Mercury, Iridium. 

Titanium, Silver, 

tained? 814. What is cadmium? 815. What are the sources of tin ? Its proper- 



CHROMIUM, ARSEXIC. 307 

§ I. Chromium, Arsenic. 

CHROMIUM. 

Sym, Or. Equiv. 26.3. 8p. Gr. 6.8. 

817. Chromium is an exceedingly hard, brittle, grayish-white 
metal, and derives its name {chroma, color) from the beautiful 
color of many of its compounds. It is rarely met with, but is 
abundant in some localities. It usually occurs as a sesquioxide in 
combination with protoxide of iron, forming the mineral chrome 
iron-stone. It also occurs in union with oxygen and lead as chro- 
mate of lead. 

818. Chromium has a strong attraction for oxygen, with 
which it forms several compounds. xVmong these the most im- 
portant is the sesquioxide Cr 2 3 , and chromic acid Cr0 3 , both 
of which resemble the corresponding compounds of iron. The 
sesquioxide is a feeble base, isomorphous.with the sesquioxide of 
iron and with alumina ; it may therefore replace either of these in 
combination. The hydrated sesquioxide is of a pale green color, 
but by ignition loses its water, and becomes of a dark green. This 
oxide is used in coloring glass and porcelain, and is the coloring 
ingredient of green-stone, the emerald, &c. 

819. Chromic Acid is interesting as being one of the constitu- 
ents of chromate of lead, the beautiful yellow pigment known as 
chrome yellow. The color of the ruby is due to the presence of 
this acid. In union with potash it forms the bichromate, a salt 
considerably used in the laboratory and in dyeing, calico print- 
ing, &c. 

ARSENIC. 

Sym. As. Equiv. 75. Sp. Gr. 5.8. 

820. Arsenic is a crystalline, brittle metal, of a steel-gray 
color and bright metallic lustre. It is found alloyed with iron, 
nickel, cobalt, copper, tin, lead, &c. ; but the chief source of the 
arsenic of the shops is mispiclcel, a double sulphide of arsenic and 
iron. The coarse, gray powder, sold under the name of fly poison, 

ties? "What is tin ware? 816. What compounds of tin are mentioned ? 817. What 
is chromium ? Why so named ? 818. What are the properties of chromium and 
its compounds ? 819. In what does the interest of chromic acid consist ? 820. State 
the properties of arsenic. What are its sources ? What is fly poison ? Effect of 



308 



INORGANIC CHEMISTRY. 



cobalt, &c, consists simply of metallic arsenic. When arsenic is 
heated in a close vessel to 356°, it volatilizes without fusion, giv- 
ing off a dense, colorless vapor, having the peculiar odor of garlic. 
If heated in the open air it takes fire, burning with a blue flame, 
and uniting with oxygen to form arsenious acid. 

821. Arsenic and Oxygen.— There are but two of these com- 
pounds: arsenious acid, As0 3 , and arsenic acid, As0 5 . The first 
constitutes the common white arsenic of the shops, the well-known 
ratsbane. It is soluble in about ten parts of hot water, the solution 
having a slightly sweetish taste and acid reaction. It also dis- 
solves readily in hot chlorohydric acid, and in solutions of the 
alkalies. Combined with copper, it forms the beautiful pigment 
known as ScheeWs green, which is used extensively in coloring 
paper hangings. Owing to its remarkable antiseptic power, it is 
used to preserve dried and stuffed specimens by collectors of ob- 
jects of natural history. Its most effectual antidotes are the 
moist hydrated oxide of iron and caustic magnesia. 

822. Arsenic Acid is formed by oxidizing arsenious acid by 
means of nitric acid. It has strongly acid prop- 
erties, decomposing the carbonates with effer- 
vescence, and readily forming salts with the alka- 
lies. Sulphur forms no less than five compounds 
with arsenic, of which the most important are 
realger or red orpiment, a bisulphide, and yel- 
low orpiment, or Tcing^s yellow, a tersulphide. 

823. Arseniuretted Hydrogen, H 3 As. — This 
gas may be formed by decomposing an alloy of 

TiTV ^ v arsenic and iron with dilute sulphuric acid, or 

U by introducing a solution of arsenic into a flask 

in which hydrogen is being evolved. It burns 

with a bluish-white flame, is highly poisonous 

and of a disgusting odor. 

824. In Maesh's test hydrogen is gener- 
ated, and if arsenic be present arseniuretted 
hydrogen is formed. Fig. 263 shows the form 

of an apparatus which answers very well for this purpose in a 
rough way. Bits of zinc and a little water are placed in the vessel, 



Fig. 263. 




Marsh's Test. 



heat upon it ? 821. What are the composition and properties of arsenious acid ? 
"What of Scheele's green? 822. Of arsenic acid ? Of the compounds of arsenic 
and sulphur ? 823. What is arsenide of hydrogen ? 824. "What is Marsh's test for 



ANTIMONY, BISMUTH, COPPEK, LEAD. 309 

which is provided with a cork through which a tube is inserted. 
Sulphuric acid is now poured in through the funnel tube, and the 
evolution of hydrogen commences. After the air has been com- 
pletely expelled from the flask, the gas may be lighted at the jet. 
If the solution containing arsenic be now poured in through the 
funnel tube, the color of the flame immediately changes, and a 
cold, white surface, held so as to cut the flame in half, is stained 
with a black or brown spot by the deposition of metallic arsenic. 
Antimony produces a similar effect, but a solution of hypochlorite 
of lime or soda dissolves the arsenical stain, leaving that made by 
antimony unchanged. This is a very delicate test, but great care 
should be taken that the sulphuric acid and zinc do not contain 
any previous traces of arsenic. 

§ II. Antimony — Bismuth — Copper — Lead. 

ANTIMONY. 

Sym. SI. (Stibium). Fquiv. 129. Sp. Or. 6.7. 

825. Antimony is a brilliant, brittle, bluish white crystalline 
metal, usually found in combination with sulphur, though it often 
occurs alloyed with other metals, and sometimes exists native. 
The principal source of the metal is the native sulphide, from 
which it is separated by heating with iron filings, or carbonate of 
potash. These combine with the sulphur, setting the metal free. 

826. Osides of Antimony. — The teroxide, Sb0 3 , is the most 
important, as it furnishes the basis of the antimonial so much used 
in medicine. Antimonic acid, Sb0 5 , readily combines with bases 
to form salts, and even unites with the teroxide, forming antimo- 
niate or antimony, or what is sometimes called antimonious acid. 

BISMUTH. 

Sym. Bi. Equiv. 210 3 . Sp. Gr. 9.8. 

827. Bismuth is a hard, brittle, reddish white metal, found 
both native and in combination. At a high temperature it is 
slightly volatile, and oxidizes rapidly. Its fusing point is 507°, but 
it forms alloys with other metals which melt below 212°. It 
forms two combinations with oxygen; the teroxide, Bi0 3 , and bis- 
arsenic? 825. How is antimony found in nature? 826. "What of its oxides? 
827. What are the properties of bismuth f What of its oxides? 828. What 



310 INORGANIC CHEMISTRY. 

muthic acid, Bi0 5 . The latter is interesting only to the chemist; 
but the former, in combination with nitric acid and water, forms 
pearl powder, the popular cosmetic. 



COPPER. 

Sym. Cu. {Cuprum). Uquiv. 31.7. Sp. Gr. 8.9. 

828. This well-known metal needs little description. It is 
tough, malleable, of a red color, and often found native in masses 
of great magnitude. Its ores are numerous and wide-spread. 
Among the most common of these is the red oxide of copper, CuO, 
and copper pyrites, a double sulphide of copper and iron. Copper is 
stiffened by hammering, and softened by heating and suddenly 
cooling in water ; the reverse of the effect produced upon steel. In 
dry air it is hardly acted upon, but in a damp atmosphere it ac- 
quires a green crust of carbonate, familiarly known as verdigris. 

829. Copper is an excellent conductor of heat and electricity, 
and is extensively used for telegraph wires. Being little affected 
by the air, it is better adapted for culinary and many other uten- 
sils than iron. Vegetable acids, however, dissolve it in the cold 
state ; hence sauces containing vinegar, and preserved fruits or 
jellies should not be allowed to remain in copper vessels, as the 
salts produced are poisonous. 

830. Oxides of Copper. — Copper forms several oxides of which 
the protoxide or black oxide, CuO, is the most important, as it 
constitutes the basis of most of the salts of copper. It is used in 
organic analysis as a source of oxygen, and in the manufacture of 
glass and porcelain to impart a green color. 

831. Sulphate of Copper, CuO, S0 3 + 5HO {Blue Vitriol).— 
This is used largely in dyeing and calico printing, and as a source 
of many of the pigments containing copper. 

832. Nitrate of Copper, CuO, N0 5 +3HO, is formed by dis- 
solving copper in dilute nitric acid. It is a very corrosive, deli- 
quescent salt, of a deep blue color, is easily decomposed, and crystal- 
lizes in prisms. 

are the most common ores of copper ? How are its properties altered ? What is 
verdigris? 829. For what is copper well adapted? What precaution is given? 
830. What is said of the oxides of copper ? 831. Of sulphate of copper ? 832. Of 



ANTIMONY, BISMUTH, COPPER, LEAD. 311 

LEAD. 

Sym. Pb. {Plumbum). Equiv. 103.6. Bp. Gr. 11.44 

833. This useful and common metal occurs under various 
mineral forms, of which the most valuable i3 galena, a sul- 
phide. Lead is a soft, blue metal, easily scratched by the nail, and 
leaving a stain when rubbed upon paper. It is highly malleable, 
but not very ductile. In the air a film of oxide rapidly forms on 
its surface, which protects it from further corrosion. It melts at 

# about 612°, and on solidifying contracts to such an extent as to 
i render it unfit for castings. 

834. If lead is exposed to the combined action of pure water 
and air, an oxide of lead is formed on the exposed surface, which is 
dissolved by the water with which it is in contact. This solution of 
oxide of lead absorbs carbonic acid, forming a carbonate of the oxide 
of lead, an insoluble but highly poisonous compound. The presence 
of chlorides or nitrates assists this corroding action, while it is re- 
tarded by the sulphates, phosphates, or carbonates. Bicarbonate 
of lime, a salt found in many spring waters, also prevents this cor- 
rosion by depositing a coating on the exposed surface. In the use, 
therefore, of lead water pipes, it should be carefully ascertained 
whether the water to be conveyed contains foreign matters, which 
will prevent its action upon the metal. 

835. Oxides of Lead. — There are four oxides of lead, the most 
important of which are the protoxide and 'peroxide. The protox- 
ide of lead, PI 0, forms the basis of the ordinary salts of this metal, 
and is the well-known powder called litharge. As it easily fuses, 
and readily dissolves silica, it is much used in glass-making and in 
glazing earthenware. The peroxide of lead, Pb0 2 , called minium 
or red lead, is consumed largely in the manufacture of flint glass. 

835. Carbonate of Lead, PbO,C0 2 (White Lead).— This salt is 
found beautifully crystallized in nature, but it is largely manufac- 
tured as a paint. It is produced in several ways, but the follow- 
ing, which is known as the Dutch method, is considered the best. 
Thin sheets of lead, rolled up into loose scrolls, are placed in 
earthen pots with weak vinegar or acetic acid. Thousands of 

nitrate ? 833. What is galena ? Properties of lead ? 834. What is the action of 
water upon lead ? How may the operation be assisted, or retarded ? In the use 
of lead pipes for water what should be determined ? 835. What is said of the oxides 
of lead ? What are the uses of litharge ? What of minium ? 836. What is car- 



312 INORGANIC CHEMISTRY. 

these pots, fitted with lead covers and closely packed, are then 
buried in spent tan bark. The acetic acid corrodes the metal, 
forming a superficial coating of acetate of lead. The carbonic acid 
set free by the decomposing vegetable matter, displaces the acetic 
acid, combining with the lead, and forming the carbonate. The 
acetic acid thus released, attacks more metal, which is again car- 
bonized, and thus, with a small charge of vinegar, the operation is 
continued a long time, and a large quantity of lead changed. 
White lead is extensively adulterated with sulphate of baryta ; it 
may be detected by adding nitric acid, which dissolves the lead,* 
leaving the baryta as an insoluble residue. 

837. Thallium is a metal recently discovered by means of 
spectrum analysis, and is found in pyrites and in native sulphur. It 
is of a brilliant white, soft, malleable, has a specific gravity of 
11.9, and resembles lead. It forms compounds with oxygen, 
chlorine, iodine, bromine, sulphur, and phosphorus — its oxides 
having a decidedly alkaline reaction. 

838. Titanium, Columbium, Tantalum, Molybdenum, Tungs- 
ten, Vanadium, and Uranium, are very rare metals, and compara- 
tively unimportant. Titanium and uranium are somewhat used for 
coloring enamels and porcelain, and the salts of the latter possess 
considerable chemical interest. 

§ III. The Nolle Metals— Mercury , Silver ', Gold, 9 
Platinum, dbc. 

MERCURY. 

Sym. Eg. {Hydrargyrum). Equiv. 100. Sp. Gr. 13.59. 

839. Sulphide of mercury, or cinnabar, is the principal source of 
this metal, though it is sometimes found native and also combined 
with silver. It has a silver-white color, a brilliant lustre, and is a 
fluid at ordinary temperatures. It' solidifies, when cooled to — 39°, 
and is then soft and malleable, but if reduced to a much lower 
temperature, it becomes brittle. It boils at about 662°, and 
slowly volatilizes at all temperatures above 40°. Metallic mer- 
cury is used extensively in the manufacture of philosophical in- 

bonate of lead ? How is it produced ? How is it adulterated ? Explain the mode 
of its detection? 837. What are the properties of thallium? 838. Of titanium 
and uranium ? 839. In what state is mercury usually found ? "What are its proper- 



THE NOBLE METALS. 313 

struments, thermometers, barometers, and as an alloy with tin for 
coating the backs of mirrors. It is also nsed largely in the ex- 
traction of gold and silver by the process of amalgamation. 

840. Oxides of Mercury.— There are two oxides of mercury. 
The first, the suboxide Hg 2 0, is of little importance. The pro- 
toxide, HgO, commonly known as the red oxide, or red jrrecipitate, 
may be formed by heating metallic mercury up to 600°, with free 
access of air. A still higher heat decomposes it, liberating the 
oxygen, and reducing the mercury to the metallic state. This 
oxide forms the basis of most of the salts of mercury, and fur- 
nishes a ready source of oxygen gas. It is the compound from 
which oxygen was first obtained by Peiestlet, and by which 
Layoisiee proved the composition of air. 

841. Chlorides of Mercury.— Two chlorides corresponding to 
the above-named oxides are known. The subchloride Hg 2 Cl, 
familiarly known as calomel, is prepared by precipitating a solu- 
tion of subnitrate of mercury with. common salt. It is a yellow- 
ish-white, tasteless, insoluble powder, used extensively in medicine. 
'The chloride HgCl, or corrosive sublimate, is formed by sublima- 
tion from a mixture of sulphate of the protoxide of mercury and 
common salt. Corrosive sublimate has a disagreeable, acrid, me- 
tallic taste, and is very poisonous. The proper antidote is white 
of egg, which forms with it an insoluble, inert compound. 

842. Sulphide of Mercury (cinnabar) occurs in large beds at 
Almaden, in Spain, and is also found in extensive deposits in 
California. It is produced in considerable quantity by artificial 
means, and sold as a pigment under the name of vermilu 

SILVER. 

Sym. Ag. (Argentum). Fquiv. 108. Sjj. 67?'. 10.5. 

843. Silver is found both native and in combination. When 
native, it occurs in fibrous, or crystalline masses ; and when com- 
bined with sulphur, it is usually associated with sulphides of lead, 
antimony, and copper. The principal mines of silver are those of 
Mexico and Peru. 

844. Preparation. — Silver is obtained from the sulphuret by 

ties? Its uses ? 840. How many oxides of mercury are there ? "What is the effect 
of heat upon the red oxide ? 841. What is the composition of calomel ? Give its 
preparation. How is corrosive sublimate formed? What is the antidote? 
B42. What is vermilion? 843. What is the appearance of native silver? With 
14 «« 



314 INORGANIC CHEMISTRY. 

roasting the ore with common salt, which converts it into a chlo- 
ride. It is then, together with water, iron scraps and mercury, 
put into casks, which are revolved on their axes. The iron re- 
moves the chlorine, and the mercury amalgamates with the silver, 
from which it is afterward freed by distillation. 

845. Silver is separated from its combination with lead by 
melting the alloy and letting it slowly cool, when the lead solidi- 
fies in crystals, leaving the silver nearly pure. It is further re- 
fined by the process of cupellation ; a cupel being a shallow, 
porous vessel, made of bone ashes. When it is melted with 
access of air, the lead oxidizes ; the oxide, or litharge melts, and 
being absorbed by the cupel, leaves the silver pure. 

846. Properties.— Silver is the whitest of the metals, with a 
bright, metallic lustre. It is very malleable, ductile and tena- 
cious. It may be extended into leaves not exceeding y^^ ff of an 
inch in thickness, and 1 grain may be drawn out into 400 feet of 
wire. Silver does not oxidize in the air at any temperature, but 
absorbs oxygen when melted, holding it mechanically and giving 
it off on solidifying. It is a good conductor of heat and elec- 
tricity, and its polished surface is one of the best reflectors of 
light. Silver is chiefly consumed in coinage and in the manufac- 
ture of silver plate. Being too soft for these purposes when pure, 
it is usually alloyed with about ^ its weight of copper, which 
gives it the requisite hardness. 

847. Oxides of Silver.— These can be formed only by indirect 
means. There are three of them, but the protoxide, AgO, is the 
only one which claims our attention. It may be made by dis- 
solving silver in nitric acid, forming nitrate of silver, and then 
precipitating it with potash. It is a dark brown or black powder, 
which forms the basis of the most important salts of silver. It is 
decomposed below a red heat, oxygen being liberated, and the 
silver reduced to the metallic state. 

848. Nitrate of Silver, AgO,]Sr0 5 . — This, the most interesting 
salt of silver, may be obtained by dissolving metallic silver in 
nitric acid ; colorless, anhydrous crystals being formed, which are 
readily soluble in an equal weight of cold water. These crystals, 

what is it associated in combination ? 844. How is it obtained from the sulphuret ? 
845. How from its combination with lead ? 846. What are the properties of silver ? 
Its uses? Why is it alloyed ? 847. What is said of the oxides of silver ? 848. How 
ia nitrate of silver obtained ? For what used ? How may the stain be removed ? 



THE NOBLE METALS. 315 

when melted and cast into small sticks, form the lunar caustic of 
surgery. Nitrate of silver stains organic matter black under the 
action of light. Advantage is taken of this property in making 
indelible ink and hair dye. A solution of cyanide of potassium 
removes the stain thus produced. 

849. Chlorido of Silver, AgCl, is occasionally found native in 
mines, and is called horn silver, from its tough, horny texture. It 
may be prepared artificially by adding a solution of common salt 
to a solution of nitrate of silver, and appears as a white powder 
which darkens in color on exposure to the air. 

GOLD. 

Sym. Au. (Aurum). Equiv. 196.4. Sp. Gr. 19.34. 

850. This is one of the most widely diffused of the metals and 
generally occurs in minute grains, though sometimes in masses 
weighing many pounds. In 1851 a lump weigh- 

ing 106 pounds was found in Australia, imbed- 
ded in a matrix of quartz. It sometimes occurs 
in crystalline form, as shown in Fig. 264. 

851. Properties. — Gold is a beautiful yellow 
metal, with a brilliant lustre and high specific 
gravity. It is the most malleable of metals, is 
exceedingly ductile, and when pure is nearly as 
soft as lead. It fuses at 2016°, and does not 
oxidize in the air at any temperature. Gold is 

,.,,,,..*; r , Crystal of Gold. 

dissolved by selenic acid, nascent cyanogen, and 
any solution that liberates chlorine ; but its usual solvent is aqua 
regia. Like silver, it is too soft for the purposes of coinage and 
jewelry when pure; the required hardness being imparted by 
alloying it with T V of its weight of copper. This alloy forms the 
standard gold for coin in this country. 

852. Carat is a term used to designate one of the parts or 
units of a certain number which is taken as the standard of pure 
gold. In the United States the number is 24, therefore pure gold 
is said to be 24 carats fine. If it contain 6 parts of alloy, it is 18 
carats fine, and so on. Assaying is the determination of the 
amount of pure metal in an alloy, or specimen of bullion. 

849. How is chloride of silver produced ? 850. "What is said of the occurrence of 
gold? 851. The properties of gold? 852. What is meant by the term carat ? What 




316 INORGANIC CHEMISTRY. 

853. Preparation. — Gold is separated from all its ores except 
silver by amalgamation with mercury. It is obtained from silver 
by boiling it in nitric acid which dissolves out the silver, leaving 
the gold pure. In this operation, in order to prevent the silver 
from being mechanically protected from the action of the acid, it 
is necessary that there should be three times as much silver as 
gold. As the gold constitutes only one quarter of the mass, the 
process is known as quartation. 

854. Gold forms compounds with oxygen, sulphur, chlorine, 
bromine, iodine, &c, but they are not of sufficient interest to re- 
quire mention. 

PLATINUM. 

Sym. PI. Equiv. 98.6. Sp. Gr. 21.5. 

855. Platinum is a rare metal, always found native, and usual- 
ly associated with palladium, rhodium, and iridium. It also occurs 
alloyed with gold, copper, iron, and lead. Its chief sources are 
the mines of Mexico, Brazil, and the Ural Mountains. 

856. Properties. — Platinum is of a grayish- white color, and 
closely resembles silver in appearance. When pure it scarcely 
yields in malleability to gold and silver ; is very ductile, and takes 
a good polish. But the qualities which render it so useful, and in 
some cases indispensable to the chemist, are its extreme difficulty 
of fusion (being unaffected by any furnace heat), and the perfect 
manner with which it resists the action of almost all acids. It 
does not oxidize in the air at any temperature, and is not acted 
upon by simple acids. It is slowly dissolved by aqua regia. 

857. We have already alluded to the power possessed by spongy 
platinum of condensing gases and causing the union of oxygen and 
hydrogen. Platinum Made is a preparation of the metal in a still 
more minute state of subdivision, and has the property of effecting 
chemical changes more energetically than platinum sponge. It 
may be produced by electrolyzing a dilute solution of the metal. 

858. With the exception of the bichloride, the compounds of 
platinum are unimportant. The bichloride of platinum is useful 
to the chemist as furnishing an excellent test for potash, which it 

is assaying? 853. Explain the preparation of gold? 854. What other compounds 
of gold are mentioned ? 855. How does platinum occur ? What are its chief sour- 
ces? 856. Its properties? Why do chemists prize it? 857. What is platinum 



ALLOYS. • 317 

precipitates from a neutral or acid solution as a double chloride of 
potassium and platinum. 

859. The remaining metals of this group, Palladium, Rhodium, 
Ruthenium, Osmium, and Iridium are rare and generally found as- 
sociated with platinum, which they resemble both in appearance 
and properties. 



CHAPTER XVII. 

SEQUEL TO THE METALLIC ELEMENTS. 

§1. Alloys. 

860. Compounds of the Metals with each other. — Metals 
combine with metals to form alloys, an important class of bodies, 
as each compound thus produced may be looked upon for many 
purposes as a new metal. These unions sometimes take place in 
equivalent proportions, but generally this is not the case. 

861. Yet the properties of alloys cannot be anticipated. Slight 
variations in the proportions of the metals produce great changes 
in the products. Alloys are always more fusible than the most 
infusible element of which they are composed, and often more so 
than any of the ingredients. Bismuth melts at 476°, lead at 600°, 
and tin at 442° ; but by combining them in the proportions of 5 
parts bismuth, 2 lead, and 3 tin, Sib Isaac Newton produced a 
fusible metal which melts below 212°. 

862. A metal of low fusibility, when melted in contact with 
one of high fusibility, causes the latter also to melt, thus acting as 
a flux. This principle is employed in soldering, or the joining two 
metals by means of a third. Pieces of gold are soldered together 
with an alloy of gold and silver ; articles of silver with an alloy 
of silver and copper ; copper with an alloy of copper and zinc 
{hard solder). 

863. Brass is an alloy of copper and zinc ; 4 parts of the for- 
mer to 3 of the latter. An increased proportion of zinc gives 
pinchbeck, Butch gold. German silver is an alloy of copper, zinc, 

black ? 858. Bichloride of platinum ? 859. What is said of the remaining metals 
of this group ? 860. What are alloys ? What is the character of these compounds ? 
S61. What is said of the properties of alloys ? Give examples. 862. What is the 



318 • INOKGANIC CHEMISTRY. 

and nickel. Bronze consists of 90 parts copper to 10 of tin ; bell 
metal and gong metal of 80 parts copper to 20 of tin. 

864. Type Metal consists of 3 parts lead to 1 of antimony ; bri- 
tannia of 100 parts tin, 8 of antimony, 2 of bismuth, and 2 of copper. 
The speculum of Lord Bosse's telescope is composed of 126.4 of 
copper to 58.9 of tin. Alloys which contain mercury are called amal- 
gams. An amalgam of tin is used for silvering the backs of mirrors ; 
and an amalgam of tin and zinc for exciting electrical machines. 

865. Alloys of Aluminum. — These promise to become very im- 
portant as the metal grows cheaper : 10 parts of aluminum and 5 
of copper form a very hard alloy, exactly resembling gold, and al- 
most as exempt from liability to tarnish. An alloy of 3 parts iron 
to 1 of aluminum does not oxidize in a moist atmosphere, and 1 
part aluminum to 9 parts copper, produces an alloy harder than 
bronze and whiter than copper. 

866. Alloys of Coin.— Gold and silver when pure are so soft 
that if coins were struck from them, they would be injured by 
wear ; hence they are alloyed to make them harder. The stand- 
ard gold of the United States coinage consists of 9 parts of pure 
gold to 1 part of alloy. As copper would darken the color of the 
gold, the alloy consists of 9 parts of copper to 1 part of silver ; 
thus 1,000 ounces of gold coin would contain 900 of pure gold, 90 
of copper, and 10 of silver. The English alloy of gold is j^ or 2 
carats ; 24 carats being pure gold. The silver coin of the United 
States is ^ silver and ^ copper ; and the new cents 88 parts cop- 
per to 12 parts nickel. 

§11. Chemistry of Photography. 

867. Eeference was made to the subject of Photography when 
speaking of the chemical action of light ; some further explana- 
tions will be suitable in this place. 

868. History. — That the salts of silver are blackened by expo- 
sure to light was known to the alchemists. Scheele, in the last 
century, discovered that this effect takes place most energetically 
in the violet region of the spectrum. Bitter, in 1801, discovered 
the independent nature of the chemical rays. The discovery 

use of alloys in soldering ? 863. What is brass ? Bell and gong metal ? 864. Typo 
metal? Amalgam? 865. What is said of alloys of aluminum ? 866. Alloys of gold 
coin. Of silver? 868. What discoveries were made by Scheele and Hitter? 



CHEMISTRY OF PHOTOGRAPHY. 319 

of photography, or light-drawing, was made by MM. Niepce and 
Dagxeeee of France, who worked jointly upon it for several years. 
Niepce dying in the meantime, it was completed and announced 
by Dagueeee in 1839, and in his honor named the Daguerrotype. 

869, The art was, however, at first far from being complete. 
The process of Dagueeee applied only to the taking of fixed ob- 
jects, such as edifices, statues, &c. ; the chemicals he employed 
being so slow in their operation that it required twenty or thirty 
minutes to take a picture. He endeavored to get an impression 
of the human face, but it came out a mere blur, and at that time 
it was believed in Europe that the art was incapable of being ap- 
plied to portraiture. Dr. J. W. Deapee of Now York, who had 
long been engaged in researches upon the chemical action of light, 
by the skilful employment of more sensitive chemicals, first suc- 
ceeded in taking portraits of the human face, by far the most in- 
teresting and important application of the art. 

870. The Daguerreotype process consists in preparing a highly 
polished silver surface, usually a plate of copper, silver-coated, and 
exposing it to vapors of iodine in the dark, when a thin yellow 
coating of iodide of silver is formed. The plate is then exposed to 
light in the camera, as has been before stated. A change takes 
place in proportion to the intensity of the light. But as the effect 
is a blackening, the lightest parts of the objects will become the 
darkest parts of the picture ; so that in the impression the lights 
and shadows of nature are exactly reversed. When the plate is 
withdrawn, the image upon it is invisible. It is then exposed to 
vapor of mercury, which is unequally condensed upon the changed 
surface ; the darkest parts receiving least mercury, the brightest 
most. The picture is now invisible, but if the plate were exposed 
to the light, the remainder of the plate would become blackened. 
It is, therefore, washed with a solution of hyposulphite of soda, 
which dissolves the remaining iodide. A little solution of the 
chloride of gold is then poured on the plate, and evaporated over 
the flame of a lamp. A thin film of metallic gold is thus deposited 
upon the surface, which improves the appearance of the picture 

Who invented the daguerreotype? 869. What was at first the imperfection of the 
art? What share had Dr. Draper in its improvement? 870. What is the first 
6tep of the daguerrean process ? How are the lights and shadows reversed ? 
What is the effect of vapor of mercury? Why is hyposulphite of soda used? 
What is the effect ? What is the effect of chloride of gold ? What are accelera- 



320 INORGANIC CHEMISTRY. 

at the same time that it aids to protect it. The first great im- 
provement consisted in introducing more sensitive chemicals, as 
chlorine, bromine, and their compounds, called accelerators, by 
which the process was quickened. 

871. The Talbotype.— Mr. Fox Talbot, of England, had been 
working upon the same subject with no knowledge of what was 
being done in France. He employed paper instead of a metallic tab- 
let ; first brushing it over with a solution of nitrate of silver, and then 
immersing it in a solution of iodide of potassium. In this way a 
surface of iodide of silver is obtained, and paper thus prepared 
may be long preserved. To render it sensitive it is washed over 
with a mixture of nitrate of silver with gallic and acetic acids, and 
after exposure in the camera, the picture is brought out by re- 
washing with the same mixture. The sensitive chemicals are 
then removed by the hyposulphites, and the picture finished by 
placing it between sheets of blotting paper, saturated with wax, 
and pressing a warm smoothing iron over the whole. 

872. Other Methods — Mr. Aecher, of England, employed 
glass tablets coated with collodion (943), in which iodide of potas- 
sium had been dissolved. It is made sensitive by placing it in a 
solution of nitrate of silver, the collodion becoming quickly im- 
pregnated with iodide of silver. M. Niepce de St. Victor coated 
the glass with iodized albumen. Ambrotyjpes are taken upon 
collodion, and finished with a balsam varnish. 

873. Pictures thus taken, where the lights and shadows of 
nature are reversed, are called negatives. But from these others 
are taken, and this reverse renders them true to nature, lights an- 
swering to lights, and shadows to shadows. These are called 
positives. Pictures are copied by placing the negative against 
a sensitively prepared surface, and exposing it to light. The parts 
protected by the dark portions of the negative then become light 
in the positive, and vice versa. 

874. Heliochromy is the term applied to the art of producing 
photographic impressions in natural colors. Several colors have 
been thus reproduced; yellow, which proved the most difficult, 
has been lately obtained. The colors are not permanent, but re- 
cent discoveries have increased their durability. 

tors? 871 ? How did Talbot prepare his paper ? What quality has it ? How is 
the picture finished? 872. What was Mr. Archer's improvement? 873. What 
are negatives and positives ? How are pictures copied ? 874. What is heliochromy ? 



PAET III. 
ORGANIC CHEMISTRY. 



CHAPTER XVIII. 

CHEMICAL NATURE OF ORGANIZED BODIES. 

§ I. Recent Progress of the Subject. 

875. Organic Chemistry is that division of the science which 
considers the chemical composition, properties, and changes of 
organic substances — or those which have originated in living 
beings — and such compounds as are derived from them. It forms 
a highly interesting and very extensive branch of the science, and 
has been chiefly created within the present century. Organic 
Chemistry, in its widest significance, embraces all that pertains to 
the chemistry of life, but it will be desirable here to limit it to the 
study of organic substances, — their compositions, properties, and 
artificial changes. The chemical relations of living beings will be 
considered in Physiological Chemistry. The present chapter will 
contain some introductory considerations on the chemical nature 
and constitution of organized bodies. 

876. Its Claims — So new is this department of investigation, 
that its position has hardly been settled. Some have denied its 
claim to the rank of a science, and consider its results uncertain 
and worthless, while others hold that it is the province of chem- 
istry not only to investigate all organic changes, but believe that 
this branch of the science must go forward until it has completely 
unravelled the mysteries of organization, and conferred upon the 
chemist the marvellous power of imitating in his laboratory the 
productions of living nature. Nor are these sanguine expecta- 

875. What is Organic Chemistry ? To what is it here limited ? 876. What dif- 

14* 



322 OEGANIC CHEMISTRY. 

tions without large warrant, when we consider the vast strides 
that organic chemistry has recently made. It will be well, how- 
ever, to define at the outset the present scope and province of 
this branch of the science. 

877. Its Past Boundaries. — Organic chemistry has hitherto 
traced the changes and investigated the products of the natural de- 
cay of living bodies. It has also destroyed organic compounds, 
varying the conditions, and thus giving rise to a host of artificial 
products. Moreoever, it was able to imitate many of the curious 
changes of living nature, transforming one organic compound into 
another of equal grade, as for example, starch into sugar. It has 
been generally believed that organic chemistry stops here ; a fun- 
damental distinction between the two great divisions of the science 
being, that while in mineral chemistry the operator can both de- 
compose and combine, in organic chemistry he can only destroy 
but cannot build up. Yital power alone, it is said, can unite the 
simpler into higher and more complex substances. This has been 
true in the past state of the science, but it is so no longer. 

878. Artificial Organic Bodies. — It has been for some time 
known that the chemist could produce a few of the lower 
organic substances. One of the earliest and most remarkable in- 
stances of organic synthesis was the artificial production of urea 
by Wohler ; but it was said of this and similar instances that 
they were n6t true, or complete syntheses, as cyanogen and am- 
monia, the substances used to start with, were organic products 
which the chemist could not directly form, and which originate 
only in the domain of life. But this objection has now lost 
its force. The chemist, in his laboratory, can create complex 
organic substances of a high order, beginning with the ulti- 
mate elements, and in his mode of doing this he seems to have 
surpassed nature herself. Carbonic acid, water, and ammonia are 
the materials which she furnishes as the starting point of organic 
construction; but the organizing plant cannot begin with the 
ultimate elements, carbon, oxygen, hydrogen, and nitrogen. 

879. Berthelot's Researches. — An unexpected and remarkable 
advancement of organic synthesis has recently been made by 

ferent views are held concerning it? 877. What was the former lim'it of the 
science ? What i3 the distinction generally made between organic and inorganic 
chemistry ? Is it a true distinction ? 878. What is said of the production of urea ? 
What can the chemist create ? 879. .State the aim of Berthelot's re- 



EECENT PROGRESS OF THE SUBJECT. 323 

Beethelot of France. This chemist has devoted himself to the 
formation of organic substances, synthetically, by combining their 
elements, through the aid of chemical forces only. In his late 
work he says : 4 We have taken for a point of departure the sim- 
ple bodies — carbon, oxygen, hydrogen, and nitrogen, and have con- 
structed, by combination of these elements, organic compounds ; 
first, binary, then ternary, &c, the former analogous to, the latter 
identical with the proximate principles contained in living beings 
themselves. The substances that we first prepare by methods 
purely chemical are the principal carbides of hydrogen — the fun- 
damental binary compounds of organic chemistry. 

880. As a means of producing all the parts from the elements 
themselves, we take oxide of carbon — a substance purely mineral — 
and by the concurrent influence of time and ordinary affinity (with 
the aid of pressure and the presence of an alkali), we thus obtain a 
first organic compound known as formic acid. This acid, united to 
a mineral base, produces a formate ; then, decomposing this for- 
mate by heat, we compel the carbon of the oxide of carbon and 
the hydrogen of the water to combine in the nascent state, and 
produce carbides of hydrogen. 

881. Artificial Production of Alcohol and Sugar. — Thus there 
is formed marsh gas, C 2 H 4 ; olefiant gas, 4 H 4 , and jnojiylene, 
C 6 H 6 . This is the first step of synthesis. The hydrocarbons thus 
prepared become the starting point for the synthesis of alcohols. 
"With marsh gas and oxygen we form methylic alcohol; with ole- 
fiant gas and water, ordinary alcohol. The artificial production 
of the carbides of hydrogen and of the alcohols constitutes the 
true difficulty ; but these once obtained by the ordinary chemical 
forces, other organic compounds become easy.' Beethelot, con- 
jointly with De Luca, has converted the hydrocarbon propylene 
into glycerin, a proximate principle of the fats ; and he has further 
transformed glycerin into one variety of sugar. 

882. Limit to Organic Synthesis. — This constructive chemistry 
will, of course, go on until many other compounds are artificially 
formed ; but there is a limit, beyond which it cannot pass. There are 
two classes of bodies found in the living world which may be distin- 

eearches. "What was the first step of the process ? 8S0. How did he produce for- 
mic acid ? What were the next bodies formed ? 8S1. Give the products of the 
first steps of synthesis. The next products. What was the chief difficulty ? "What 
other bodies did Berthelot and De Luca form ? 882. "What two classes of 



324 ORGANIC CHEMISTRY. 

guished as organic and organized. The first, as acetic acid, sugar, 
and alcohol, resemble inorganic bodies in having a definite com- 
position, and many of them take on a crystalline form. Organized 
bodies, on the contrary, are less definite in composition, never 
crystallize, and have rounded outlines ; they have an organized, 
structure, as seen in the vegetable leaf and animal muscle. We 
have no reason to suppose that this class of bodies can ever be 
produced by methods of art. 

§11. Constitution of Orgcmio Compounds. 

883. To draw an exact line between organic and inorganic 
chemistry is impossible ; indeed the latest and most purely sci- 
entific treatises, as those of Beethelot and Oddling, entirely 
ignore the distinction. Yet, there are certain marked peculiari- 
ties which contrast organic substances with those which we have 
been considering. In the first place, they are much less perma- 
nent, more mobile and changeable. Plants and animals rapidly 
grow, and as rapidly decay. "While they live they are the theatres 
of incessant change, and when life ceases, the transformations go 
swiftly forward till dissolution carries back the materials to the 
fixed, or inorganic state. This is a fundamental condition of or- 
ganization, and chemistry has thrown much light on its causes. 

884. The Organic Elements. — While inorganic chemistry is 
concerned with the entire array of elementary substances, organic 
chemistry deals with but few of them. Of the 64 elements, only 
four, viz., carbon, oxygen, hydrogen and nitrogen, compose the 
chief mass of the vegetable and animal kingdoms. Besides these 
elements, organized bodies contain also a small proportion of 
mineral matter — the ash that is left after they are burned. It 
consists of ten or twelve elements forming metallic bases, acids, 
and salts, as are shown by the Chart and Atlas. 

885. Complexity of Organic Substances. — The list of organic 
compounds is almost endless, and is rapidly extending. It is an 
interesting question how, from three or four elements, such a mul- 
titude of substances, with so infinite a diversity of properties^ can 

bodies are found in the living world ? To what is constructive chemistry limit- 
ed? 883. What is said of the distinction between organic and inorganic chem- 
istry? What fundamental distinction is mentioned? 884. Name the chief or- 
ganic elements. 885. What interesting question is suggested ? What is the com- 



CONSTITUTION OF ORGANIC COMPOUNDS. 325 

arise. Nothing like it is to be found in inorganic chemistry. 
While mineral substances consist of but few atoms, organic com- 
pounds contain a great number. Thus an equivalent of potash 
has 2 atoms, carbonic acid 3, and ammonia 4, while sugar contains 
34 atoms, stearine 236, and albumen nearly 900. "We have, there- 
fore, a reason for the instability of organic substances. As com- 
plicated machinery is always most easily deranged, so, in chemis- 
try, the more complex a substance, the more readily is the balance 
of its affinities disturbed by slight causes. The large-atomed 
organic masses are thus easily decomposed into a host of simpler 
compounds. 

886. Contrasts of the Elements.— A further cause of insta- 
bility is seen in certain remarkable contrasts of properties ex- 
hibited by the organic elements. Thus, while carbon is the most 
invincible of solids, and cannot be liquefied by any amount of heat, 
the other three are equally invincible gases, and cannot be con- 
densed into liquids by the intensest cold, aided by many thousand 
pounds' pressure on the square inch. While carbon manifests the 
strongest atomic cohesion of all the elements, hydrogen is its ex- 
treme antithesis, exhibiting the most perfect mobility of atoms. 
Again, while oxygen manifests the widest and intensest range of 
attractions of all the elements, nitrogen is the very type of inert- 
ness and indifference. 

887. Each Element Influences the Compound. — We trace in 
organic compounds the influence of the prevailing elements. Car- 
bon is the universal solidifying constituent. It exists in all organic 
substances, so that organic chemistry was defined by Laurent as 
4 the chemistry of carbon compounds.' But if carbon imparts 
solidity, the gases with which it is associated give fluency and 
mobility. Organic compounds thus have a freedom of change 
which is variable, but intermediate between the unchangeable 
carbon and the volatile gases. Carbon imparts combustibility, as 
does also hydrogen in a still greater degree. The class of bodies 
in which these elements predominate — the hydrocarbons — are 
the most inflammable, and a portion of the class have a dietetical 
value based upon this character. 

888. Nitrogen imparts non-combustibility and changeable- 

parison as to number of atoms? Examples. Why are organic "bodies unstable? 
886. How are the organic elements contrasted? 887. "What influences organic 
compounds? Examples. How did Laurent define organic chemistry? What 



326 



ORGANIC CHEMISTRY. 



Fig. 265. 




ness ; — the nitrogenous group burn with difficulty, and are very 
prone to decomposition. The act of forming organic substances 
consists in liberating them from oxygen, so that they may be re- 
garded as high in the organic scale just to the degree in which 
they are freed from this element. Those having an excess of 
oxygen, as the vegetable acids, are of the lowest organic grade. 
"We here see a cause of class-diversities among organic sub- 
stances. 

839. Influence of Composition — Of course organic compounds 
will vary in properties with varying com- 
position. Thus, if we remove from alcohol 
the elements of an atom of water, it is 
changed to ether ; if it lose a little hydro- 
gen, it is converted into aldehyd ; and if it 
then acquire a little oxygen, it becomes 
acetic acid — the proportions of carbon re- 
maining all the time unchanged. 

890. Isomerism and Allotropism — 
Another and inexhaustible source of diver- 
sity among organic compounds is believed 
to be the grouping of their constituent atoms. Organic chemistry 
furnishes abundant and varied evidence of the operation of this 
principle, numerous bodies being con- 
vertible into each other without loss 
or addition, by the mere regrouping 
of their atoms. In Fig. 265 the cir- 
cles represent atoms, and their succes- 
sive rearrangements may illustrate 
the altered grouping of a compound. 
Figs. 266 and 267 show the isomerism 
of woody fibre and gum, and how their 
difference of properties may be caused. Another 
source of the diversity of properties and plasticity of organic 
compounds, is very probably the remarkable allotropic variations 
of their constituents. "We have seen how marked this property is 
in sulphur, oxygen, and phosphorus. Carbon, also, the universal 
and essential constituent of organic compounds, has its threefold 

is said of their freedom of change? 888. What property does nitrogen impart ? 
What affects the properties of organic substances? Example. 890. How docs 
isomerism explain diversities of organic bodies ? Allotropism ? 891. What distinc- 



Illustration of Isomerism. 



Fig. 266. 

KH© 

Ki© 

Woody Fibre. 



Fig. 267. 





Gum. 



COLLOID CONDITION OF MATTER. 327 

aspect. That the elements carry their allotropic conditions into 
combination seems to have been lately established by Beodie, who 
has succeeded in producing several compounds of carbon in which 
it evidently exists in the state of graphite (528). See Atlas. 

§ III. Colloid Condition of Matter — Dialysis. 

891. — The recent distinction of bodies into crystalloid or crys- 
tal-like, and colloid or jelly-like, has been stated ; but the view is 
of such importance in connection with organic phenomena as to 
require further explanation. 

892. Their Contrasted Properties. — It was said that the crys- 
talloids as water, acids, saline compounds, sugar, &c, tend to as- 
sume hard forms with angular outlines ; that they are easily 

♦soluble, and form solutions which are mobile, or without viscidity. 
Colloid bodies, on the contrary, as albumen, gum, glue, starch, 
&c, are soft, with rounded outlines, have little or no tendency to 
crystallize, are slowly soluble, and form viscid solutions. 

893. Power of Diffusion. — In this respect there is a further 
important contrast of properties. This may be shown by pro- 
viding two jars and placing in one a little colored crystalloid, as 
bichromate of potash, and in the other a colored colloid, as caro- 
mel (burnt sugar). If each be covered several inches deep with 
another colloid, as starch jelly for example, after a few days it will 
be observed that the potash salt has diffused upward through the 
gelatinous mass, while the caromel has hardly discolored the jelly 
immediately above. This experiment illustrates a most important 
general principle, viz. : that crystalloids diffuse actively through 
colloids, and that colloids will not diffuse through each other. 

894. Dialysis — These facts open a new source of analysis. If 
a small hoop be prepared and one side of it be covered with strong 
paper (942), it forms a vessel like a sieve. Let this be floated upon 
pure water, and a mixture of crystalloids and colloids, as sugar and 
gum, be placed upon it. The paper is a colloid, and the crystal- 
lized sugar will diffuse rapidly through it into the water below, 
while hardly a trace of gum will pass. Any animal membrane, or 
a layer of gum, gelatine, or albumen, when used as a partition, acts 

tion of bodies is important in organic chemistry ? 892. Give some of their contrasted 
properties. 893. What are their powers of diffusion. What does this experiment 
illustrate ? 894. Describe the experiment with the sieve. What is this mode of 



328 ORGANIC CHEMISTRY. 

in the same manner, transmitting crystalloids and arresting col- 
1 loids. Prof. Geaham calls this mode of separation dialysis. 

895. A New Theory of Osmosis — These views afford a new 
explanation of osmose (70). Geaham maintains that it is not true 
capillary attraction which causes the flow of liquids through moist 
memhranes, as formerly described, but that it is due to a combi- 
nation and decomposition taking place in the membrane. When a 
colloidal membrane is in contact with pure water upon one side, 
and a saline solution on the other, it combines with the water, 
but the saline solution, having a stronger attraction for the 
water than the membrane has, takes it away, and thus, by a con- 
stant hydration and dehydration of the intervening colloid, the 
motion of the currents is established. 

896. Further Contrasts. — There are still other contrasts be- 
tween these two classes of bodies which throw light upon organic 
changes. The crystalloids are of a permanent nature, while the 
colloids are unstable. The former, from their hardness, are com- 
paratively unaffected by external agencies, while the latter, from 
their softness, are extremely susceptible to them. As might be 
supposed, the living body is formed of soft, impressible colloids, 
albumen, gelatin, fibrin, &c. As the colloids cannot diffuse into 
each other, they are adapted for fixity of structure ; while, from 
their ready permeability by water containing crystalloid mate- 
rials, they give rise to the motion of fluids. 

897. Mutability of Colloids. — Moreover, while the chemical 
equivalents of the crystalloids are generally low, those of the col- 
loids are always high. The crystalloids have a decided taste, and 
are chemically active, while the colloids, from their high equiva- 
lents, and the massiveness of their complex atoms, are chemically 
inert, and insipid to the taste. But, physiologically, these relations 
are exactly reversed. The colloids are the seat and instruments 
of change ; they not only impel the circulations ; but, from their 
complexity and mutability, they are themselves capable of those 
rapid decompositions and transformations which are necessary 
for the manifestation of the vital actions. Having contributed 
for a while to the stability of the structure, they break up into the 

analysis called ? 895. What is Graham's new theory of osmose ? How are the 
osmotic currents established ? 896. State other contrasts between crystalloids and 
colloids. How do these properties affect the living body? 897. How do crystal- 
loids and colloids differ chemically ? How physiologically ? 899. What docs prox- 



ORGANIC ANALYSIS. 



329 



simpler forms of crystalloids, and then rapidly diffuse away as 
waste products. 

898. Speaking physiologically, the crystalloid has been termed 
the statical condition of matter, and the colloid the dynamical. 
Gkaham remarks that the colloids possess caergia, and may be 
looked upon as the primary source of the force appearing in the 
phenomena of vitality. 



Fig. 268. 



§ IV. Organic Analysis. 

899. Proximate Analysis determines the proportions of the 
proximate principles of organic bodies ; for example, the starch, 
sugar, gluten, ligneous fibre, and oily matter in the flour of wheat. 
The first step consists in thoroughly drying the substance to be 

analyzed by exposure to a heat of from 
212° to 250° in an oven with double 
sides, inclosing water, brine, or oil, to 
maintain a steady temperature, which 
is indicated by a thermometer, Fig. 
268. The proportions of water and 
solid matter are thus ascertained. 
The dried product is then exposed to 
the action of various substances in 
succession. Water dissolves sugar 
and gum, ether the fatty bodies, al- 
cohol various crystallizable organic principles, such as vegetable 
alkalies ; while diluted acids and alkalies are employed to effect 
other solutions ; they must always be used cautiously, however, 
as they tend to decompose organic matter. 

900. Use of the Microscope. — In this kind of analysis the mi- 
croscope is of great use in determining the completeness of sep- 
aration, as it is often better fitted for the detection of organic par- 
ticles than any chemical tests that can be applied. For this reason 
the microscope has been made to do excellent service in the de- 
tection of adulterated mixtures of food. 

901. The Mineral Elements of organized bodies are procured 
by taking a weighed portion of dry organic matter and carefully 




Drying Oven. 



imate analysis determine ? TVhat is the first step ? What the next process ? 
900. Is the miscroscope nsefal? 901. How are the mineral elements procured? 
902. In what does ultimate organic analysis consist ? 903. Describe the apparatus 



330 



ORGANIC CHEMISTRY. 



burning away the combustible part. The ash that remains is then 
submitted to the action of various solvents, and its several ingre- 
dients ascertained. 

902. Forms in which Elements are obtained. — As the chief 
bulk of most organic substances consists of carbon, oxygen, hydro- 
gen, and nitrogen, ultimate organic analysis consists in determining 
the proportion of these elements. They may be obtained either 
separately or in a state of combination, but the latter method is 
most practicable. Nitrogen is generally produced in the form of 
ammonia ; hydrogen as water, and carbon as carbonic acid. 

903. The Apparatus of Analysis.— The analysis of a body con. 
taining carbon, oxygen, and hydrogen is effected in the following 
manner : A sheet iron furnace in the form of a trough, A, Fig, 
269, rests upon bricks, g g. A tube known as the combustion tube, 

Fig. 269. 




Apparatus for Organic Analysis. 

half an inch in diameter and fifteen inches long, rests upon sup? 
ports iu the furnace. This is closed at one end, and filled with dry 
oxide of copper mixed with the substance to be analyzed. Oxide of 
copper is used because it readily imparts oxygen to combustibles 
in contact with it, but when heated alone, it bears a very high tern-, 
perature without being decomposed. This tube is tightly connect-, 
ed by a cork to the drying tube, which is filled with chloride of 
calcium, and accurately weighed ; f represents Liebig's potash 
bulbs which contain solution of caustic potash. These are also care- 
fully weighed and attached to the drying tube by air-tight con- 
nection. 

904. The Process.— The combustion tube is surrounded with 
charcoal and heated to redness. A portion of the oxygen of the 
copper, seizing upon the hydrogen of the organic body, forms 



for organic analysis. 904. Describe the process. 905. How is the oxygen de- 



ORGANIC ANALYSIS. 331 

water, which, passing off as vapor, is either condensed at d, or 
absorbed by the chloride of calcium. Another portion of the 
oxygen, combining with the carbon, forms carbonic acid, which, 
passing through the drying tube, enters the bulbs, and is absorbed 
by the potash. When the combustion is complete, the potash 
tube is detached and weighed, the gain being in carbonic acid, 
three tenths of which is carbon. The chloride of calcium tube is 
also weighed ; its increase is water, one ninth of which is hydro- 
gen. As there is no other source for the carbon and hydrogen 
than the organic body, the quantity which it contained is thus 
determined. 

905. Determining the Oxygen.— But the carbon and hydrogen 
together do not equal the weight of the original substance ; the de- 
ficiency is ash and oxygen. The proportion of ash being ascer- 
tained by incineration of another sample, the quantity of oxygen 
is the remaining deficiency, and is easily calculated. 

906. Determining the Nitrogen. — If the compound to be ana- 
lyzed contain nitrogen, its quantity must be determined by a sep- 
arate process. When heated in a suitable apparatus with an ex- 
cess of hydrate of potash, the whole of the nitrogen escapes in the 
form of ammonia, which is easily collected, weighed, and the pro- 
portion of nitrogen determined. 

907. Of course this is but the barest outline of the process, 
and is designed only to convey a general idea of the mode of pro- 
cedure. Numberless precautions and particulars of the most del- 
icate nature have to be observed, and only a consummate skill of 
manipulation can produce trustworthy results. 

908. Organic Equivalents. — The information furnished by bare 
analysis is but scanty; it does not give the combining propor- 
tions of a compound, or the number of its atoms. To obtain these, 
the unknown substance must be made to unite with some com- 
pound, the constitution of which is established. Various well- 
determined mineral substances are used — very frequently oxide of 
silver, which combines with many organic bodies. Its equivalent 
is Agl08 + O8 = 116. If it be desired to determine the combining 
number of acetic acid, a weighed portion of the oxide is made to 
unite with the acid, of which it takes an equivalent quantity. 



lermined ? 906. How the nitrogen ? 907. What is necessary to obtain trustworthy 
results ? What does bare analysis fail to give ? 908. How are organic equivalents 



332 ORGANIC CHEMISTEY. 

Suppose that the acetate of silver formed amounts to 48.73 grains. 
It is then burned. The acetic acid and the oxygen of the silver, 
are both driven off, the loss being 17.24 grs., and there are 31.49 
grs. of pure metallic silver left. Then 

Amount At. wt. Amount At. wt. 

of silver. of silver. of acid. of acid. 

31.49 : 108 : : 17.24 : 59 

This product, 59, is, however, too high, as it includes the oxygen 
of the silver, which escapes with the acid. Deduct this, and we 
have 51 as the true atomic weight of acetic acid. 

909. Calculating Formulae.— If now, by the process (904), 
we analyze the same quantity of acetic acid, we shall find that it 
contains 24 parts carbon, 3 hydrogen, and 24 oxygen. These 
quantities divided by the atomic numbers of the elements, give 4 
equivalents of carbon, 3 of hydrogen, and 3 of oxygen, or C 4 H 3 03 } 
as the empirical formula of acetic acid. 

§ V. Theory of Compound Radicles* 

910. Importance of Grouping. — The recent advance in chem- 
istry compels us to the conclusion that the arrangement of atoms 
is of more significance than either their proportions or their kinds. 
Formerly organic compounds were classified according to their 
obvious properties, as acids, bases, &c. ; but at the present time 
the strict scientific method is to distribute them into groups and 
series according to relationships of derivation and analogies of 
atomic arrangement. The doctrine is worked out in different 
ways by different authorities, and though chiefly of importance 
to the advanced chemist, it will be also interesting to the general 
student, as developing many curious facts and illustrating the direc- 
tion of progressive thought. 

911. Compound Radicles have been referred to as combina- 
tions of elements, which play the part of simple bodies, so that we 

* " The German term radikal is commonly but inaccurately translated radical^ 
which is properly an adjective, the word radicle being the appropriate rendering." 
(Miller.) 

obtained ? How is the combining number of acetic acid obtained ? 909. How is the 
formula determined ? 910. What is said of the arrangement of atoms ? How were 
organic compounds formerly classified ? What is the present strictly scientific 
method ? 911. What are compound radicles ? Give the combinations of the simple 



HOMOLOGOUS SERIES. 333 

may trace them in their relations and changes as we do the ele- 
ments themselves. Potassium, for example, is an element; it com- 
bines with oxygen, forming oxide of potassium KO, and this again 
combines with water, forming KO, HO, or hydrated oxide of potas- 
sium. If, in place of water, nitric acid be used, we have nitrate 
of oxide of potassium, KO, N0 5 , or with other acids, a large class 
of salts of oxide of potassium. Potassium is here regarded as the 
starting point, the root, or radicle, of this series, and, being un- 
decomposable, it is called a simple radicle. 

912. Example. — Now there are compounds or groups of ele- 
ments which behave in a similar way, and are hence called com- 
pound radicles. Ethyl, for example, is a radicle with the composition 
C 4 H 5 , and gives rise to a series of compounds, like potassium : thus, 

Ethyl, C 4 H 5 

Oxide of ethyl (wine ether), C 4 H 5 , O 

Hydrated oxide of ethyl (common alcohol), C 4 H 5 , O, HO. 

As potassium combines with sulphur, chlorine, iodine, etc., to 
form a series of salts, so ethyl combines with the same elements to 
form a series of ethers, as follows : 

Oxide of potassium, KO Oxide of ethyl, C 4 H 5 O 

Sulphide of potassium, KS Sulphide of ethyl, C 4 H 5 S 

Chloride of potassium, KC1 Chloride of ethyl C 4 H 5 CI 

Iodide of potassium, KI Iodide of ethyl, C 4 H 5 I 

Bromide of potassium, KBr Bromide of ethyl, C 4 H 5 Br 

In the last column we have a series of ethers, in which S, 
CI, I and Br replace the O of common ether. Other compound 
radicles, as methyl (C 2 H 3 ) and amyl (O 10 H n ), give rise in the 
same way to different series of ethers and alcohols. 

913. It was at first objected to this theory that the radicles 
were hypothetical bodies, which could not be separated or proved 
to exist. To this it is replied, that several of them hate teen sep- 
arated, while the view they afford greatly assists the comprehen- 
sion of organic changes. See Chemical Atlas and Chart. • 

§ YL Homologous Series. 

914. Homology is a term used to express an interesting rela- 
tion among organic substances, which has been made by Geehardt 

radicle potassium. 912. In what way do compound radicles act ? Example. 913. 
"What objection was made to this theory ? How answered ? 914. What is Ger- 



334 ORGANIC CHEMISTRY* 

the basis of classification in his system of chemistry. A series 
of compounds is called homologous when each member of it — that 
is, each compound — differs from the others in a regular manner, 
either by a uniform number, as 2 H 2 , or its multiple; and when 
the properties of these different compounds are entirely analogous, 
yet differ in degree in proportion to the varying composition. 

915. There is a class of compounds, for example, known as 
alcohols, which manifest a close analogy with each other, both in 
composition and in their modes of decomposition. In the sub- 
joined table the composition and homology of the most important 
of this group of bodies is represented. 

Homologous Seeies of Alco- Homologous Seeies of Vola- 

hols. tile Acids. 

Methylic alcohol, C 2 H 4 2 Formic acid, C 2 H 2 4 

Common alcohol, C 4 H 6 2 Acetic acid, C 4 H 4 4 

Propylic alcohol, C 6 H 3 2 Propylic acid, C 6 H 6 4 

Butylic alcohol, C 8 H 10 O 2 Butyric acid, 8 H 8 4 

Amylic alcohol, C 10 H 12 O 2 Yalerianic acid, G 10 H 10 4 

Caproic alcohol, C 12 H, 4 2 Caproic acid, C 12 Hi 2 4 

Oaprylic alcohol, 0, 6 R x 8 2 Caprylic acid, C l6 R l6 4 

Laurylic alcohol, 24 H 26 2 Laurie acid, C 24 H 24 4 

Cetylic alcohol, 32 H 34 2 Ethalic acid, C 32 H 32 4 

Cerylic alcohol, 54 H 56 2 Cerotic acid, 54 H 54 4 

Melissylic alcohol, O 60 H 62 2 Melissic acid, C 60 H G0 4 

Here it will be seen that the first six of the alcohols differ by 
the successive addition of 2 2 , and the rest by its multiples, 
Formulas have been constructed to represent these compounds in 
which n n stands for 2, 4, 6, 40, or any even number of atoms of 
carbon and hydrogen, and by which the composition of the al- 
cohols is indicated, thus C n H n+2 2 . 

916. When any compound of a homologous series is decom- 
posed, it gives rise to compounds which are definitely related to 
it, but as they are differently constituted, they are termed hetero.- 
logous compounds. The alcohols, when decomposed, give rise to 
a serfes of ethers, of aldehyds, and of acids ; — heterologous groups, 
but each forming a homologous series. The most complete of 
this series is that of the volatile acids, some of which are given in 

hardt's basis of classification ? What is a homologous series of compounds ? 915. 
Example. How do these compounds differ? How are they represented in for- 
mulae ? 916. What are heterologous compounds ? Example. What is the most 
complete of this series, and from what derived ? What is their difference and for- 



THEORY OF TYPES. - 335 

the table. They are derived from the alcohols by oxidation, and 
several of them occur in nature. They differ by an increment of 
C 2 Ho. and have the following general formula, CnH n 4 

917. The extreme terms of this series are widely separated in 
properties ; formic acid being a pungent, corrosive, volatile liquid, 
which must be cooled to 32° to solidify it, while melissic acid is a 
solid fat which melts at 192°. But if we compare any compound 
of the series with the adjoining ones, the difference in properties 
will be found but slight. They increase in solidity, and their 
melting and boiling points rise gradually with each successive in- 
crease of the common difference. But a part of the series is 
given in the table ; it rises uninterruptedly, step by step, from 
2 to 38 equivalents of carbon and hydrogen, through nineteen 
links of the homologous chain ; above this there are gaps not yet 
filled. A few years ago only the first two members of the series 
were known. For illustrations of this and the following subject, 
see the Chemical Atlas. 

§VII. Theory of Types. 

918. Convinced of the difficulty of representing the actual ar- 
rangement of the atoms of chemical compounds, many chemists 
maintain that we should represent in formulas only those relations 
and analogies among compounds which result from their modes of 
decomposition, when subjected to the action of the same chemical 
reagents. To effect this, all substances are thrown into a few 
great classes of analogues, and some leading member of each divis- 
ion, having familiar and well-marked characteristics, is selected as 
the pattern or type of the class, from the formula of which that 
of all the others is derived. This view puts resemblance of chemi- 
cal properties out of the question ; hence the same type may com- 
prehend acids, bases, and neutral bodies. 

919. Geehaedt refers most of the bodies of organic chemistry 
to four principal types, as follows — the first column representing 
the types, and the second giving single examples of compounds 
arranged under them : 

mula? 917. What is said of the extreme terms of this series? How do the com- 
pounds differ successively? "What is further said of this series? 918. "What do 
many chemists maintain in regard to formula? How is this result obtained? 
What is further said of this view ? 919. What are G-erhabdt's four principal 



336 ORGANIC CHEMISTRY. 

1. The hydrogen type, g j or H 2 *%$&*> hydride ° f Me " ° 2 g 3 [ 

2. The chloride or HI ™ , , , ■ , u C 4 H, | 
Chlorohydric acid type, CI [ Chlorohydnc ether, «gf f 

3. The oxide or H ) ^ A . , . C 4 H 5 ) 2 
Water type, H \ ° 2 Alcohol > H [ 

4. The nitride or § ) M „ rt , . C ^ 5 ) v 
Ammonia type, gj" N Ethylamine, 1 j-N 

920. Substitution and Replacement. — When the idea of a type 
is accepted, the changes that take place under it are regarded as 
replacements or substitutions. It is like preserving the general 
structure of an edifice, though constantly removing its individual 
bricks and stones and replacing them by others. Thus in the 
chloride type we can substitute for the chlorine, iodine, bromine, 
or cyanogen, while the type remains unaltered. 

921. Perhaps the most interesting case of substitution is where 
ammonia is converted into a complex organic base by replacing its 
hydrogen with various compound radicles. If bromide of ethyl be 
made to act upon ammonia, a new base ethylamine, C 4 H 7 N, appears. 

This is a compound of the ammonia type, H > 1ST, and may be repre- 

H) 
4 H 5 ) 
sented thus, H > N" ; that is, it is ammonia in which one atom 

H ) 
of hydrogen has been displaced by its equivalent of ethyl, C 4 H 5 . 

If this new compound be heated with bromide of ethyl, diethylamine 

C 4 H 5 ) 
is obtained, 4 H 5 >N"; that is, another atom of hydrogen is re- 

H ) 
placed by an atom of ethyl. Again, the last atom of hydrogen may 

be replaced by the radicle, and triethylamine results, C 4 H 5 > N". 

C 4 H 5 ) _ 
Thus a new ammonia is formed, closely resembling in properties 
common ammonia. 

922. Another remarkable instance of this substitution is that of 
chlorohydric ether, 4 H 5 01. Chlorine combines with this ether, 
forming a series of five new compounds, in which it displaces the hy- 

types ? 920. How are changes that take place under a tj^pe regarded ? What com- 
parison is made ? Example. 921. What remarkable case of substitution is given ? 
What is the composition of ethylamine ? Diethylamine? Triethylamine? 922. 



THEORY OF TYPES. 337 

drogen, equivalent for equivalent, until the latter element is all re- 
moved, and the compound completely chlorinated. Neither the 
number of atoms in the compound, nor their arrangement are 
changed in this complete revolution of composition, while the 
boiling point and density steadily rise as the quantity of chlorine 
increases. 

923. Coupling of Organic Compounds. — We have just seen 
that there is a class of substances produced by the union of two or 
more simple organic compounds, yet retaining the character of one 
and losing that of the other. Thus, ethyl unites with ammonia, 
its own characteristic properties disappearing, while those of am- 
monia continue. The terms coupling, or conjugation of com- 
pounds, have been applied to this kind of union, while that con- 
stituent whose properties disappear is called the copula. 

924. The foregoing views are not sufficiently developed to 
serve as a basis of popular classification. We shall adopt an ar- 
rangement less strictly scientific, but more convenient for the 
general student. 

The chief vegetable and animal products, and their most im- 
portant changes, will be noticed in the following order : — 

1. The saccharine and amylaceous group. 

2. The oleaginous group— fats and oils. 

3. Acids, loses, and coloring principles. 

4. Nitrogenous compounds, their changes and products. 

5. Animal products. 

6. Chemistry of foods. 

7. Chemistry of soils. 



CHAPTER XIX. 

THE SACCHARINE AND AMYLACEOUS GROUP. 

925. This is an important class of organic bodies, composing 
the chief bulk of the vegetable kingdom, and entering largely into 
the diet of animals. They are distinguished by several chem^ 

Give another case of this substitution. How is the compound affected by this 
revolution ? 923. What is coupling of compounds ? 924. What is said of these 
views ? 925. What is the relation of the saccharine and amylaceous group to the 
15 



338 ORGANIC CHEMISTRY. 

ical peculiarities. Containing no nitrogen, they are termed 
the non-nitrogenous group ; being composed of three elements, 
carbon, hydrogen and oxygen, they are known as the ternary 
group ; and, as they contain hydrogen and oxygen in the exact 
proportion to form water, they have been called hydrates of car- 
ton. We cannot say, however, that the hydrogen and oxygen 
exist in these compounds as water. Their mode of origin and 
mutual relations in the plant will be noticed in the chapter 
on vegetable growth. 

§ I. The Sugars. 

926. These sweet-tasted bodies are widely distributed through 
the vegetable kingdom, and largely employed as food. There are 
several varieties of sugar, but we can notice only three : cane 
sugar, or sucrose; grape sugar, or glucose; and milk sugar, or 
lactose. 

927. Cane Sugar, C 12 H n On {Sucrose.) — This, the most im- 
portant variety, has a specific gravity of 1.6, is soluble in one third 
its weight of cold water, forming a thick sirup, and is the sweetest 
of all the sugars. When evaporated from its solutions it readily 
crystallizes ; but when long boiled it acquires an atom of water, loses 
its property of crystallization, and acquires an acid reaction. If 
boiled for some hours, with a trace of acid added, it is changed to 
grape sugar, C 12 H 12 12 + 2 Aq. In its chemical relations sugar 
ranks with acids; it dissolves and combines with various bases, 
forming saccharates ; as 2PbO, C 12 rI 1() O 10 , saccharate of lead. 
Sucrose melts at about 320°, and by cooling forms the transparent, 
amber-colored solid known as oarley sugar. If the melted sugar 
be heated to 420°, a brown, bitter mass results, known as caromel, 
which is much used by cooks and confectioners as a coloring agent. 

928. Manufacture of Sugar. — Cane sugar is chiefly produced 
from the cane, beet root, sorghum, and the palm and maple trees ; 
but by far the largest portion is from the sugar cane. The canes 
are crushed by passing them between grooved iron cylinders. 
The juice, when first expressed, is liable to rapid decomposition 

vegetable and animal kingdoms?. How are they named, and why? 926. What 
are the sugars? Their varieties? 927. Give the composition of cane sugar. 
Properties. How is it changed to glucose? What are saccharates? Caromel? 
928. From what is cane sugar produced? Give the mode of its manufacture. 



THE SUGARS. 339 

from the heat of the climate. This is prevented by the addition 
of a small quantity of lime, which neutralizes acids and coagulates 
impurities. The juice is evaporated by boiling in large open ves- 
sels, and when reduced to a proper consistency, is transferred to 
coolers, where a portion of it crystallizes, forming raw, or brown 
sugar. On an average, a gallon of juice produces a pound of 
sugar. 

929. Molasses. — The drainage of the raw sugar forms molas- 
ses. It contains a portion of the sugar that has been burnt and 
darkened in boiling, another part that has been changed to the 
uncrystallizable state, and still another of crystallized sugar. 
It has a strong, peculiar taste, and is acidulous. It is very 
absorbent of water ; indeed many kinds of raw sugar, from this 
cause, melt into sirup when exposed to the air. 

930. Refining of Sugar. — Crude sugars are purified, or refined, 
by reducing them to a sirup and first filtering it through twilled 
cotton, to separate mechanical impurities. The same effect is 
further promoted by the use of serum of blood. To decolorize the 
sirup it is again filtered through a bed of coarsely-powdered 
charcoal. It is then evaporated in vacuum pans — the air being 
exhausted, so that it will boil at a lower temperature — and finally 
re crystallized. 

931. Grape Sugar, C 12 H 12 12 +2Aq. {Glucose).— This variety 
of sugar is less soluble and less easily crystallized than sucrose. 
We are familiar with it as the sweet grains of raisins, figs and other 
dried fruits, and it is also largely obtained by transformation of 
starch (951) ; hence it is called starch sugar. Bernard has shown 
that it is normally produced in the livers of animals, and it appears 
as a morbid constituent of the urine in the disease called diabetes. 
The candied sugar of honey and sweetmeats consists of glucose. 
Fruit sugar was formerly supposed to be a distinct variety, but it 
proves to be rather a mixture of different kinds. 

932. Milk Sugar, C 4 H 24 24 (Lactose), is obtained only from 
the milk of the mammalia, to which it gives its sweetish taste. It 
is obtained by evaporating clarified whey till it crystallizes. It is 
much less soluble, and, therefore, much less sweet than cane or 
grape sugar, and its crystals are hard and gritty. 

929. How is molasses obtained? What are its properties? 930. How is sugar 
refined ? 931. How does grape sugar differ from sucrose ? From what is it ob- 
tained ? "What is fruit sugar? 932. "What is milk sugar, and how obtained? 



340 



ORGANIC CHEMISTRY. 



II. Starch. 




Starch Grains of Potatoes. 



Fig. 271. 




Starch Grains of Plantain. 



Fig. 270. 933. Starch, 0, 2 H 10 O 10 (Fecula, 

Amadin). — This substance is found 
universally distributed in the vege- 
table kingdom in grains, seeds, roots, 
and the pith and bark of plants. 
When pure it is a snow-white glis- 
tening powder. Examined by the 
microscope, it is found to consist 
of exceedingly minute round, or 
oval grains, which vary in size 

from T ^o to xoloo °f an mcn m 
diameter. Potato granules are much 
larger than those of wheat or rice. 
Starch grains from different sources 
vary also in form and structure. 
Those of the potato are egg-shaped ; 
those of wheat are lens-shaped ; those 
of rice angular, while several kinds 
have a grooved aspect, and consist 
of concentric layers, like the coats 
of an onion. As each variety has 
some peculiarity by which it may be 
identified, the adulteration of wheat 
flour by potato, or other starches, 
may thus be detected. 

934. Properties — Starch is in- 
soluble in cold water, alcohol and 
ether, but swells up, and is con- 
verted into a paste in water containing 2 per cent, of alkali. If 
heated in water to 140°, the grains swell and burst, producing a 
jelly-like mass (gelatinous starch, or amadin), which is used 
to impart a gloss to textile fabrics. The test of starch is iodine, 
which combines with it, forming a blue compound. 

935. Sources and Varieties. — Starch is largely procured from 
potatoes, wheat, and rice. Corn starch is obtained from Indian 

Properties 933. Give the composition of starch. "Where is it found? Ita 
appearance? State the differences in starch grains. 934. What are the prop- 
erties of starch ? Its test ? 935. Give the sources and varieties of starch. 



Pig. 272. 



•J* 









Starch Grains of Rice. 



STARCH. 341 

corn by chemical agency, being freed from the glutinous, oily, and 
ligneous elements of the seed, by the aid of alkaline solutions, and 
by grinding and bolting the corn in a wet condition. Sago is a brown- 
ish-white starch, obtained from the pith of the palm tree. Tapioca 
and arrow root are starches from the roots of West India and South 
American plants. 

936. Transformations of Starch. — When commercial starch is 
heated under pressure to 320°, it becomes soluble in cold water, 
and is changed into gum. It is sold under the name of British 
gum, and is successfully substituted for gum arabic by calico 
printers in thickening their colors. If gelatinous starch is boiled 
for a few minutes wirh weak sulphuric acid, it changes from a 
viscid mass to a limpid fluid, and a substance is produced called 
dextrine, which resembles gum in properties. It is a transparent, 
brittle solid, isomeric with starch, soluble in water, incapable of 
fermentation, and produces right-handed rotation in a ray of polar- 
ized light ; hence its name. If the acid solution of dextrine is boiled 
for some hours, and the acid removed by neutralizing it with 
chalk and filtering, the liquid will be found to yield upon evapora- 
tion a mass of solid glucose exceeding in weight the starch from 
which it was produced. The starch has become grape sugar, 
C 12 H 14 14 , its increase in weight being due to the acquisition of 
the elements of water. The sulphuric acid suffers neither change 
nor loss, but seems to effect the transformation by its bare pres- 
ence. Unripe fruits contain starch, which by ripening is con- 
verted into sugar. 

937. Gum, C^H^On (Arabin). — These terms are applied to 
a class of substances which are often seen exuding in globular 
masses from the bark of trees, as the plum and cherry. Gum is 
translucent, tasteless, inodorous, and either dissolves in water, or 
swells up and forms with it a thick mucilage. It exists in small 
proportion in the cereal grains, but its chief source is tropical trees, 
from the bark of which it flows in such quantity as to be gathered 
for commercial purposes. Gum Arabic, the product of a species 
of acacia, is a hard, brittle substance, and is, perhaps, the best 
known of the gums. Its solution being very adhesive, is used as 

936. What is British gum, and how used? How is dextrine produced? Give 
its properties. How is it changed to grape sugar? What of unripe fruits? 

937. What is gum or arahin ? Its sources and properties. What is gum arabic ? 



342 



OKGANIC CHEMISTRY. 



a substitute for paste or glue. Mucilage or dassorin (O l2 E. l0 O lQ ) 
is a kind of gum insoluble in water, but which swells into a gela- 
tinous mass when moistened. It abounds in gum tragacanth, and 
also in quince seeds and linseed. 

938. Vegetable Jelly, Pectin, or Pectic Acid, is a substance 
resembling starch and gum in its composition, which gives to the 
juices of fruits and roots the property of gelatinizing. When 
boiled a long time it loses its gelatinous property, and becomes of 
a gummy nature. It is but slightly nutritive. 



§ III. Woody Fibre. 




939. Cellulin, C 12 H 10 O 10 .— This is the most abundant prod- 
uct of vegetation. Besides forming the chief bulk of all trees, it 
F IG . 273. exists in the straw and stalks of 

grain, in the membrane which 
envelops the kernel (bran), in 
the husk and skin of seeds, and 
in the rinds, cores, and stones 
of fruit. Wood consists of slender 
fibres, or tubes closely packed 
together. Fig. 273. When first 
formed these tubes are hollow 
and serve to convey the sap, but 
in the heart wood of trees they 
become filled up and consoli- 
dated as shown in Fig. 274, the 
circulation of fluids taking place 
in the white external sap wood 
(alburnum). Upon the density 
with which the fibres are im- 
bedded together depends the 
property of hardness pr soft- 
ness of wood. 

940. Composition and Prop- 

Ceilulin is the fibrous 

the base of the woody tissue. It has been known as cel- 



Celis aud Air Passages of Vegetable 
Tissue. (Gray.) 

Fig. 274. 




Tubes of Heart Wood. (Gray.) 

erties. — "Woody fibre consists of two parts, 
portion- 



Mucilage? 938. What is said of pectin? 939. Give the composition of cellulin. 
Where is it found? How is wood formed? Upon what does its hardness de- 
pend ? 940. Of what is the fibrous portion of wood composed ? State the prop- 



WOODY FIBRE. 343 

lulose, but it is better, as Miller suggests, to change it to cellulin, 
reserving the termination ose for the sugars. Cellulin, when pure, 
is white, tasteless, and insoluble in water, alcohol, or ether, but 
dissolves in a solution of oxide of copper in ammonia. It is nearly 
pure in cotton, linen, and elder pith. In the tissue of cellulin 
there is deposited a ligneous incrustation called lignin, which is 
the thickening and hardening constituent of wood, and forms the 
principal part of its weight. It is difficult to separate and has not 
been obtained pure, nor has its composition been determined. It 
is deposited mixed with the coloring matter of the wood and with 
resinous substances, which increase its combustibility. 

941. Transformations of Cellulin. — Cellulin is not colored 
blue by iodine, but when digested for a short time in sulphuric 
acid, it is changed and answers to the test of starch. It may be 
converted into sugar by the following process. Two parts of linen 
and cotton threads are soaked for 24 hours in three parts of sul- 
phuric acid, and the mixture is then largely diluted with water 
and boiled for a few hours. If the acid be then neutralized with 
chalk, a mass of glucose is obtained which, if the process is well 
conducted, may exceed in weight the woody fibre employed. 

942. Paper is made chiefly from waste cotton and linen rags. 
They are bleached, boiled in alkali, and reduced to pulp by means 
of a beating engine. The pulp, formed into sheets and dried, is 
blotting paper. To convert it into writing paper, it is soaked in a 
preparation of glue and alum (sized), and then pressed between 
hot iron plates. To make vegetable parchment, thin, unsized paper 
is plunged for a few moments into a mixture of sulphuric acid and 
water, and then washed. In some unknown way the fibre is 
affected and the paper made live times stronger than before the 
process. 

943. Gun Cotton, C 36 H 21 9ND 41 O 303 Pyroxyline.—U cotton, 
linen, sawdust, or paper is dipped into a mixture of equal meas- 
ures of sulphuric and nitric acid, of sp. gr. 1.520, a remarkable 
chemical change takes place : 9 atoms of the hydrogen of the cel- 
lulin are replaced by 9 equivalents of peroxide of nitrogen (X0 4 ), 
while the fibre, without being changed in appearance, increases in 
weight 82 per cent. When removed from the solution and prop- 
erties of cellulin. What of lignin ? 941. Describe the changes of cellulin. 942. 
How is paper made ? Blotting and writing papers ? How is vegetable parchment 
prepared? 943. What is the composition of gun cotton? How is it prepared? 



344 ORGANIC CHEMISTRY. 

erly washed and dried, it forms gun cotton, discovered a few years 
ago by Prof. Schoxbeix. It ignites at 400° (200° below gunpow- 
der), and disappears in an instantaneous flash, leaving hardly a 
trace of residue. Authorities vary in estimating its explosive 
force, but the latest make it about three times that of gunpowder. 
The extreme suddenness of the propulsive force overstrains the 
gun and produces less effect upon the ball than gunpowder. Col- 
lodion is formed by dissolving gun cotton in ether containing a 
small proportion of alcohol. On evaporating the ether, a trans- 
parent, adhesive film is left, which is insoluble in water and is used 
in surgery for protecting wounds from the air. The chief use of 
collodion, however, is in photography. 

§ IV. Destructive Distillation of Wood. 

944. "When wood is heated in close vessels, or with but partial 
access of air, it gives rise to a large number of compounds, depend- 
ing upon the nature of the wood and the temperature employed. 
The products of distillation at the lowest temperature, as water and 
acetic and carbonic acids, contain much oxygen. As the tempera- 
ture rises the products contain less oxygen, as creosote, and wood 
spirit. At a higher heat various hydrocarbons appear, as eupion, 
paraffin, while at a red heat pure hydrogen predominates. A 
residue of charcoal always remains in the retort; in dried hard 
wood amounting to 25 per cent, of its weight, or § of the carbon 
which the wood contained. 

945. Charcoal and Tar.— Charcoal is commonly prepared by 
covering piles of wood with earth, so as partially to exclude the 
air. The mound or pit is then fired, and the volatile constituents 
of the wood gradually distilled off, by a slow, smothered combus- 
tion, leaving the charcoal. To produce tar, resinous pine woods 
are used, and the bottom of the pit made concave. As the com- 
bustion proceeds, the liquid products are separated, collect at the 
bottom, and flow out through a trough into a reservoir. They 
consist of tar, acetic acid, and oil of turpentine. "When tar is dis- 
tilled, essence of turpentine is separated and pitch remains. 

By 'whom was it discovered? How does it compare -with gunpowder? How is 
collodion prepared? What are its uses? 944. What occurs when wood is heat- 
ed in close vessels? Mention the successive products. What is the residue? 
945. How is charcoal prepared? How is tar produced? What of the liquid 
products? 946. How is pyroligneous acid obtained? State its properties and 



DECAY OF WOOD A!NT> ITS PRODUCTS. 345 

946. Pyroligneous Acid or wood vinegar, is best obtained 
from dry beech wood, a pound yielding nearly half a pound of the 
acid. It is a brown liquid, with a strong smoky taste and odor, 
and contains acetic acid. It is extensively used to form salts — 
the acetates used by dyers. 

947. Creosote (flesh-preserver) is a colorless, oily liquid, with 
a smoky odor and burning taste. It is a powerful antiseptic, and 
meat steeped for a few hours in a solution of 1 part creosote to 
100 parts water, remains sweet, and will not putrefy. Creosote is 
used very extensively in medicine, both inwardly and as an exter- 
nal application, but an over-dose is a corrosive poison. Crude 
pyroligneous acid, on account of the creosote it contains, is used 
to preserve meats, to which it imparts a smoked flavor. The 
curing quality of the smoke of green wood is also owing to this 
cause. It is the vapor of creosote which renders smoke so irri- 
tating to the eyes. 

948. Paraffin.— -This is a product of the distillation of wood, 
but is procured chiefly from coal. It is a hard, white, tasteless, 
inodorous, crystalline solid, resembling spermaceti. It melts at 
111°, and is formed into beautiful candles, which burn with a 
bright flame, like those of the finest wax. It is a pure hydrocar- 
bon, having the same composition as olefiant gas. 

949. Wood Spirit — Wood Naphtha — Methylic Alcohol, are 
names given to a product of the distillation of wood. It is a 
limpid, inflammable, colorless liquid, with a spirituous odor and 
burning taste. It is chiefly used to dissolve the resins in making 
varnish. A host of compounds, as eupion, a light, volatile oil, and 
pittacol, a deep-blue solid, have the same origin. 

§Y. Decay of Wood and its Products. 

§50. By exposure to the air and moisture, the woody matter 
of plants undergoes a slow decay. In this process of eremacausis 
oxygen is absorbed, and carbonic acid and water formed ; but as 
the hydrogen is taken first, the carbon remains, and the vegetable 
mass gradually darkens in color, and is converted into a brown, 
or black mould. The term humus is generally applied to the crum- 

uses. 947. What is creosote ? Its uses ? What of crude pyroligneous acid ? 
Of smoke? 948. Describe paraffin. Its properties and use. 949. Name some 
other products of the distillation of wood. 950. How is woody matter affected 
15* 



346 ORGANIC CHEMISTRY. 

bled vegetable matter in a state of advanced decay, and as dis- 
tributed through the soil. It is of an acid nature, and in its 
several stages different acids are produced, as geic, humic, and 
ulmic acids. This class of substances is of great importance in 
soils, as by their decomposition they yield carbonic acid to plants, 
while they have the power of absorbing and retaining ammonia 
to be yielded up for the same purpose. 

951. Organic Matter of Soil. — Carbonaceous matter constant- 
ly accumulates in the soil of forests, which proves that it is derived 
from the atmosphere, and that growth is more rapid than decay. 
It is removed from soils by cropping, and restored by adding vege- 
table and animal manures; by ploughing in fresh plants (green 
manuring), or by cultivating those which have many roots in the 
earth. A crop of clover was found to leave in the soil several 
thousand pounds weight of roots, while wheat did not yield one fifth 
this quantity. In the temperate zones, where decomposition pro- 
ceeds slowly, the decay of aquatic plants in marshy places produces 
thick beds of carbonaceous matter, which are known as peat logs. 

952. Mineral Coal. — At the delta of the Mississippi, and the 
mouths of other great rivers, masses of drifting wood are con- 
stantly being buried in the mud, and undergoing slow carboniza- 
tion. Something like this, but on a larger scale, and under 
varying circumstances, has taken place in the past history of the 
globe. Mineral coal was formed in the earth from an ancient 
vegetation ; the trees — whether grown upon the spot, or collected 
into basins by floods — were covered with mud, and carbonized by 
a slow, smouldering decomposition. Lignite is a kind of imperfect 
coal which, though found in the tertiary strata and buried many 
ages ago, is yet in the early stage of the process. It is of a brown 
color, and retains to a considerable extent its woody structure. 
"When first raised, it contains a large proportion of moisture. In 
Mtuminous coal the process is more complete, having reached the 
hydrocarbon stage ; it consequently burns with flame, and when 
heated with exclusion of air, is converted into color. Anthracite rep- 
resents the last stage of change ; all volatile matter is expelled, car- 
bon and ash alone remain, and it consequently burns without flame. 

by heat and moisture? What is humus? Mention the products of its decay. 
What are their uses? 951. What accumulates in forests, and what does it prove? 
How is it removed, and how restored ? How do peat bogs originate ? 952. What 
is constantly occurring at the mouth of the Mississippi ? How has mineral coal 
been formed ? What is lignite ? What of bituminous coal ? Of anthracite ? 953. 



MINERAL OILS. 347 

953. Mineral Hydrocarbons.— In addition to the coals, there is 
found in the earth a class of highly inflammable bodies, liquids, 
semi-liquids, and solids, which are closely connected in properties. 
The purest and most fluid form of these hydrocarbons is known as 
naphtha ; when of the consistence of oil, it is called petroleum ; 
when still thicker, it is pitch ; the next grade is elastic bitumen, 
and in its most indurated state it is termed asphaltum. Naphtha is 
a solvent for bitumen and caoutchouc, and is also of use to the 
chemist in preventing the oxidation of potassium and sodium. 

954. Mineral Oils. — In many parts of the earth naphtha, petro- 
leum, and other oils of various consistence ooze to the surface of 
the ground, or are procured from wells sunk a few feet. Petro- 
leum is found impregnating the strata in the vicinity of fire-formed 
rocks and also in masses, as the pitch lake of Trinidad, three miles 
in circumference and of unknown depth. The petroleum from the 
shores of Seneca Lake, 1ST. Y., was known to the Indians under the 
name of Seneca Oil. In one province in Asia several hundred 
thousand hogsheads are annually obtained. 

955. — "Within a short time it has been found that mineral oil is 
procurable in many places in the United States and Canada, and 
the discovery has suddenly given rise to a lucrative and important 
business. Wells are sunk in the manner of the Artesian borings 
for water, by drilling through the rocks, often to the depth of. 
several hundred feet. In some instances the oil rises to the surface 
from the pressure below, but generally it is pumped up by a steam 
engine. The oils of different localities vary in character. They 
are of a greenish, reddish, or dark aspect, and have a disagreeable 
odor. They are mixed with water or' brine; are accompanied by 
inflammable gases, and when purified yield from 25 to 90 per cent, 
of a light oil fit for illumination. The heavier oil, which is unfit 
for this use, is mixed with lard oil and employed for lubricating 
machinery. 

956. Origin of the Cil. — These substances are probablv natu- 
ral distillations from organic bodies by the aid of heat. It is diffi- 
cult to see how they can be derived from the coal, for when pro- 
cured in the same locality, the wells are in many cases sunk 

Mei tion other hydrocarbons found in the earth State the uses of naphtha. 954. 
How do these liquid hydrocarbons occur? Whrr? is petroleum found? 955. 
Where hare mineral oils been discovered, nnd what has resulted ? How are they 
obtained? What further is said of them? 956. What is the supposed origin 



348 0EGA1STIC CHEMISTRY. 

through the coal bed to the sandstones and shales beneath. In 
K W. Pennsylvania and New York the wells are ontside the coal 
fields, and the oil-bearing strata dip south and pass 500 or 600 feet 
below the coal measures. Oil fountains in different parts of the 
world issue from all the stratified rocks, but the bituminous shales 
are probably their chief source. 

957. Coal Oil is a product of the distillation of bituminous 
coal, bituminous shales, and asphalt. The material is placed in iron 
retorts, in large pits, holding a hundred tons, or in kilns of brick 
containing twenty-five tons. The retorts are heated from without, 
like gas retorts, while the kilns are fired within, like the tar pits 
(945). Some coals produce 130 gallons of crude oil per ton, yield- 
ing 75 gallons of refined oil, while others do not yield a third of 
this quantity. The first product collected in the reservoirs resem- 
bles the natural oil from the wells, and is refined by the same 
method. It is first distilled at a temperature of 600° or 800°, 
and the product, conveyed to cisterns holding 3,000 gallons, is agi- 
tated with 5 or 6 per cent, of sulphuric acid. The acid and settled 
impurities being drawn off at the bottom, the mass is again agitated, 
first with water, and afterward with alkaline lye ; it is then re- 
distilled. 

958. Coal products. — The products of the distillation of coal 
v are numberless ; we can mention but a few. Coal naphtha is ob- 
tained from the distillation of coal tar, and is purified in a similar 
manner to coal oil. Benzole or benzine is a limpid oily liquid 
somewhat resembling oil of turpentine. It is a ready solvent of 
caoutchouc, gutta percha, wax, camphor and fats, and is exten- 
sively used for removing grease stains from silks and woollen arti- 
cles. If a current of moist air be passed through benzole, it ab- 
sorbs so much of the vapor that it may be conveyed to a distance 
and burned like illuminatiDg gas. Nitro-benzole results from dis- 
tilling benzole with nitric acid, and resembles oil of bitter almonds 
so closely as to replace it in perfumery. Carbolic acid is an 
abundant crystalline product of the distillation of coal, resembles 
creosote, and has the property of augmenting friction in a high 
degree — the opposite effect of the oils. "When placed between a 

of these oils? "Why are they probably not derived from coal? What is 
the chief source of oil fountains? 957. What is coal oil, and how prepared? 
What is said of the yield ? How are the oils refined ? 958. What of coal 
naphtha? Describe benzole. Its uses. Nitro-benzole. Carbolic acid. Car- 



FATS AND FIXED OILS. 349 

knife blade and a dry oilstone, it causes them to bite and bind, as 
if there were powerful cohesion. 

959. Beautiful Dyes from Coal Tar. — From the refuse of the 
gas house, long held as worthless, chemistry has lately extracted a 
series of the most beautiful dyes. The basis of these colors is 
aniline, itself a base of the ammonia type. The radical phenyl re- 
places an atom of 

C l2 H 5 ) 
the hydrogen ; thus H > N = aniline. It is a colorless, limpid 

H ) • 
fluid, of an agreeable, vinous odor and burning taste. It combines 
with acids, forming a long series of salts which are perfectly analo- 
gous to the salts of ammonia. From these salts several most beau- 
tiful colors have been produced of different shades of purple, violet, 
and pink. Mauve, magenta, and an exquisite blue known as lieu 
de Paris, are aniline colors. 



CHAPTEE XX. 

THE OLEAGINOUS GROUP. 

§ I. Fats and Fixed Oils. 

960. Oily bodies are generally divided into two classes, fixed 
and volatile. The former do not evaporate at ordinary tempera- 
tures, and are decomposed by heat, while the latter volatilize on 
exposure to the air, and are distilled by heat. "We shall here ex- 
tend the group to include resinous compounds. 

961. Identity of Oils and Fats.— The fats and fixed oils are a 
class of compounds having nearly the same chemical composition 
and properties. They are composed of carbon, hydrogen, and 
oxygen ; the hydrogen being usually present in excess, with but 
a small proportion of oxygen. The difference between an oil and 
fat is simply one of temperature, as a slight accession of heat 
changes the solid fat to the liquid oil without altering its essen- 

bazotic acid. 959. What has been obtained from gas house refuse ? What is ani- 
line, and how composed ? Give its properties. Name some aniline colors. 960. 
Into what are oily bodies divided, and how are they distinguished? 961. Give 
the composition of fats and oils. What is the difference between them? 962. 



350 ORGANIC CHEMISTRY. 

tial properties. What the Africans call palm oil, and know only 
as a liquid, we term palm butter, because in this country it is a 
solid. 

962. Properties. — These bodies, when pure, are clear, trans- 
parent, and either colorless or slightly yellow. The peculiar odor 
some of them possess is owing to the presence of volatile acids ; 
thus butter contains butyric acid; goat's fat, hircic acid; and 
whale oil, phocenic acid. They are usually bland and mild to the 
taste, are greasy to the touch, and when placed on paper, render 
it semi-transparent, leaving a periflknent stain. They do not 
evaporate in the air, and are all decomposed by the action of heat. 
Consisting almost entirely of carbon and hydrogen, they have, of 
course, a strong attraction for oxygen, and are therefore highly 
combustible. In consequence of their combustibility, and the 
large amount of light which they emit, they are universally used 
as a source of illumination. 

963. Constitution of Fatty Bodies. — The fats and oils were 
discovered by Chevreul to consist of several proximate principles, 
known as stearin, margarin, and olein, which are each capable of 
separating into an acid and a base. The base is the same in all, 
and is known as glycerin. Stearin consists of glycerin, combined 
with stearic acid, C 3G H 3C 4 . In margarin, glycerin is united 
with margaric acid, C 34 II 34 4 , and in olein, with oleic acid, 
36 H 34 4 . Thus the oils must be regarded as having the con- 
stitution of salts. The consistence of fatty bodies is due to the 
relative proportions of these proximate principles. 

964. Glycerin, C 6 H G 6 , so named from its sweet taste, is, 
when pure, an inodorous, transparent, colorless sirup. It is 
readily soluble in water and alcohol, and is a powerful solvent 
and antiseptic. Of late years, it has been employed as a medi- 
cine ; and, on account of its solvent power, it is also largely used 
as a vehicle for administering other medicines. It is extensively 
employed in the manufacture of cosmetics and perfumery. Gly- 
cerin is non-volatile, and when heated over 600°, is decomposed, 
and gives off a peculiar acrid substance termed acroleine. This is 
the body which causes the irritating fumes of a smouldering can- 
dle wick and of burning fats, when the combustion is incomplete. 

State the properties of fats and fixed oils. To what is their odor due ? What of 
their combustibility ? 963. How are fatty bodies constituted? To what is their 
consistence due ? 964. Give the composition and properties of glycerin. Its uses. 



THE DRYING OILS. 351 

965. Olein is that portion of oil which causes its fluidity; 
hence it is more abundant in oils than in fats, and in the fat of 
swine, than in the harder tallow of the sheep or ox. It is ex- 
pressed on a great scale from lard, for burning in lamps, and for 
other uses. 

966. Stearin and Margarin.— Stearin gives to certain fats and 
oils the opposite quality of solidity. It is most abundant in tallow 
and suet, and is obtained by subjecting them to great pressure in 
flannel or hair bags, between hot iron plates, when the olein sepa- 
rates and flows away. The solid stearin thus procured is exten- 
sively used for the manufacture of stearin candles. Oils which 
are liquid at common temperatures contain but a small proportion 
of stearin, as may be shown by subjecting them to the action of 
snow or ice, when the stearin is deposited and the olein floats 
above. Margarin resembles stearin in its property of hardness ; 
it exists in human fat, butter, olive oil, &c, and may be seen in 
the thick deposit made by olive oil when subjected to a low tem- 
perature. 

§11. The Drying Oils. 

967. The fixed oils are divided into two classes : the drying 
oils, or those which harden on exposure to the air, and the 
unctuous oils, or those which remain soft and greasy when simi- 
larly exposed. , The hardening of the oils is due to the absorption 
of oxygen. 

968. Linseed Oil is the most important of the drying oils, and 
is obtained by expression from the seeds of the flax plant, which 
yield it in the proportion of from 20 to 25 per cent, of their 
weight. The drying property, upon which its value depends, is 
greatly increased by boiling for some hours with litharge, the 
product being known as toiled oil, or drying oil. The change 
wrought consists in depriving the oil of certain gummy, mucila- 
ginous matters dissolved in it, which combine with the litharge, 
and are precipitated as a white sediment. Mixed with various col- 
oring matters, chiefly metallic oxides, linseed oil forms paint, and 
it is also used in making varnish. If, after boiling for a time, 
linseed oil is ignited and allowed to burn for half an hour, it ac- 

What of acroleine? 965. Describe olein. 966. What of stearin? Of margarin? 
967. How are the fixed oils divided ? 968. How is linseed oil obtained ? How may 
its drying property be increased ? Explain the change. Its uses. How is printer's 



352 OEGANIC CHEMISTRY. 

quires a viscid, tenacious consistence, and, by the addition of a 
due quantity of lampblack, forms printer's ink. 

969. Drying oils expressed from walnuts, poppy seeds, hemp 
seeds, &c, are employed in the manufacture of paints and varnish. 
Croton oil is expressed from the seeds of a plant grown in India. 
It is a thick brown oil, and a powerful purgative. Cool liver oil is 
extracted from the liver of the codfish, and is largely used in 
medicine. It contains phosphorus, bromine, and iodine (each in 
combination with some organic substance), and also a small propor- 
tion of the constituents of the bile. Sperm oil, procured from the 
spermaceti whale, has considerable drying properties, and is much 
used iu illumination. 

970. Castor Oil is obtained from the seeds of the castor oil 
plant. Its principal use is in medicine, but it is also employed in 
the manufacture of printing ink, and in perfumery. It hardens 
after long exposure to the air, and thus forms a connecting link 
between the drying and unctuous oils. 

§ III. The Unctuous Oils. 

971. These remain soft and sticky when exposed to the air. 
This property renders them very valuable for diminishing the fric- 
tion of rubbing surfaces, as the axles of carriages and other 
machinery, a purpose to which the drying oils are not adapted. 
For the same reason the unctuous oils are worked into leather to 
maintain it in a soft and pliable condition. The unctuous oils and 
fats are liable to turn rancid on long exposure to the air ; that is, 
they absorb oxygen and generate acids which emit a disagreeable 
odor. This change appears to result principally from minute 
quantities of nitrogenized organic tissues which remain diffused 
through the fats. They are purified by sulphuric acid. "When added 
to oil, it first attacks its nitrogenized and other impurities, but if 
too much acid is used, the oil itself is decomposed. 

972. Olive Oil, or Sweet Oil is obtained by pressure from the 
fleshy parts of the fruit of the olive tree. It contains 72 per cent, 
of olein and 28 of margarin, the latter of which congeals in cold 

ink made? 969. What other vegetable drying oils are mentioned? Mention 
the constituents of cod-liver oil ? What of sperm oil ? 970. Of castor oil ? 971. 
What property distinguishes unctuous oils, and how are they used? What is 
said of their rancidity ? How are they purified ? 972. How is olive oil obtained ? 



VOLATILE OR ESSENTIAL OILS. 353 

weather. As it is less apt to become viscid than most other oils 
by exposure to the air, it is preferred for greasing delicate ma- 
chinery. In Southern Europe it is extensively used as a substitute 
for butter. 

973. Palm Oil is expressed from the fruit of the palm tree, 
and is of an orange-yellow color. It contains 70 per cent, of olein 
and 30 per cent, of a peculiar fat resembling margarin, which is 
termed palmatin. It is largely employed in the manufacture of 
soap and candles. The oil of sweet almonds is mainly used in oint- 
ments, liniments, and soaps. Colza oil, or rape oU, is obtained 
from the seeds of a plant belonging to the cabbage family. It is 
extensively employed for illumination, and is also used for lubri- 
cating machinery. 

974. Train Oil, or Whale Oil, is obtained from the fat of va- 
rious fishes, as the whale, dolphin, and the seal. It is of a yellow 
color, and not of a disagreeable odor unless the fish were putrid, 
or the oil expressed by a strong heat. It is used for illumination, 
to oil leather, in medicine, and in soap making. 

975. Spermaceti is a solid fat which is found in the head of the 
sperm whale in connection with sperm oil. Pure spermaceti is a 
beautifully white, crystalline substance, somewhat unctuous to the 
touch, and resembles white wax in lustre and hardness. It is em- 
ployed for making candles, and in pharmacy as an ingredient in 
ointments. In this fat the ordinary base glycerin is replaced by 
another, termed etJial. 

976. Butter is the oily portion of milk, and is a mixture of several 
fats, the principal of which are margarin and butyrolein. Bromeis 
found in 100 parts of butter 68 parts of margarin, and 30 of buty- 
rolein, the remainder being outyrin, caproin, and caprylin, com- 
pounds of butyric, caproic, tmd caprylic acids, with glycerin. The 
characteristic odor and flavor of butter are owing to the presence 
of these latter substances. 

977. Human Fat is soft, yellowish, and without odor. Its solid 
constituent is principally margarin, with a proportion of palmatin 
and olein. The bodies of persons that have been for years buried 
in churchyards are sometimes found to have been changed into a 
peculiar substance resembling fat, and termed adipocere. It is also 

Give its composition and uses. 973. From, what is palm oil procured ? State 
its composition and uses. What of colza oil ? 974. For what is whale oil used ? 
975. What of spermaceti ? 976. Of what is butter composed ? 977. What is 



354 ORGANIC CHEMISTRY. 

formed when the bodies of animals are exposed to running water 
till the muscular and membranous parts have been washed away. 
It has been shown that this substance is the original fat of the 
body, which has resisted decomposition, and is partly in the state 
of a fatty acid, and partly saturated by ammonia, with traces of 
lime and magnesia. 

§ TV. Volatile or Essential Oils. 

978. These differ in many particulars from the fixed oils. They 
readily volatilize, and are usually possessed of a strong odor and 
hot, pungent taste. They make only a transient stain upon paper, 
do not form soaps, and are all of vegetable origin. They dissolve 
in alcohol, ether, and acetic acids, and mix readily with the fixed 
oils. Their solution in alcohol is termed an essence, hence the 
name essential oils. 

979. Preparation.— These oils are generally obtained by dis- 
tilling portions of the plant with water. The steam, as it passes 
over, carries with it the oil, although the boiling point of many of 
them is higher than that of water. The water and oil condense 
together, most of the oil floating upon the surface. A small pro- 
portion, however, is retained in solution by the distilled water 
which gives it the odor and taste of the essence. These solutions 
are termed ' perfumed waters,' as rose water, lavender water, &c. 
In some cases the oil is obtained by expression directly from the 
cells which contain it, as from fresh orange and lemon peel. In 
other cases, where the oil is so. delicate as to be destroyed by dis- 
tillation, it is extracted by placing the plant or flower between 
layers of cotton, or of woollen cloth, saturated with some fixed 
oil. This gradually absorbs the volatile oil of the plant, and a 
fragrant essence is prepared by digesting the cotton in alcohol. 
The specific gravity of these oils varies from 0.847 to 1.17. 

980. Composition of the Volatile Oils.— They generally con- 
tain two proximate principles, viz., Stearopten, the solid constit- 
uent, and fflaopten, which has a liquid consistence. In reference 
to their ultimate composition they are usually divided into three 
classes: 1st, those composed of carbon and hydrogen only; 2d, 

the composition of human fat? "What is adipocere ? 978. How do volatile 
differ from fixed oils ? Why are they so named ? 979. How are they obtain- 
ed? "What are perfumed waters? In what ways are essential oils prepared? 
980. "What is their composition. How are they divided ? 981. For what is the 



VOLATILE OR ESSENTIAL OILS. 355 

those composed of carbon, hydrogen, and oxygen ; and 3d, those 
which contain sulphur and nitrogen in addition to the last named. 

981. The first class includes fifteen or twenty bodies that are 
remarkable for their isomerism. Thus, the oils of turpentine, 
lemons, oranges, juniper, copaiba, citron, black pepper, and sev- 
eral others which have widely different properties, possess exactly 
the same composition — 100 parts of each containing 88.24 of car- 
bon and 11.76 of hydrogen. 

982. Oil of Turpentine (Spirits of Turpentine) may be taken 
as a type of this class of substances. It is obtained by distilling 
with water the pitchy matter that exudes from the pine tree. The 
portion remaining after distillation is common rosin. Oil of tur- 
pentine is a colorless, limpid fluid, having a strong odor and dis- 
agreeable taste. It boils at 320°, and has a specific gravity of 0.86. 
It is highly inflammable and when purified is used for illuminating 
purposes, under the name of camphene. Burning fluid is rectified 
turpentine, or camphene dissolved in alcohol, which increases 
the proportion of hydrogen and renders it less smoky when burned. 
Turpentine is also used in varnishes as a solvent for resins and gums. 
Hydrochlorate of camphene or artificial camphor is obtained by 
passing a current of dry chlorohydric acid through oil of turpen- 
tine. It is a white, crystalline solid, closely resembling common 
camphor. 

933. The second class, or those oils containing oxygen, in- 
cludes among others, common camphor, the oil of bitter almonds, 
and the oils of cummin, cinnamon, anise seed, peppermint, roses, 
lavender, &c. 

984. Camphor is extracted by distilling the wood of the cam- 
phor tree (found in Japan and other parts of the East), with water, 
and collecting the vapors in a vessel containiug rice straw. It 
condenses in the straw and is again sublimed, after which it is 
thrown into commerce ; but it requires subsequent purifications to 
fit it for use. Camphor is quite volatile and readily soluble in al- 
cohol, with which it forms a solution known as spirits of camphor. 
Taken in large doses it acts as a poison. 

985. Black mustard seed, onions, horseradish, hops, &c., yield 
oils containing sulphur and belong to the third class. Many of 

first class remarkable? Examples. 982. What is oil of turpentine? Rosin? 
Burning fluid? Artificial camphor? 983. "What does the second class include? 
984. How is camphor obtained ? What is spirits of camphor ? 985. What is said 



356 ORGANIC CHEMISTRY. 

them are characterized by pungent, unpleasant odors, which are 
readily observable in the breath after eating substances containing 
them. 

§ Y. Resinous and Waxy Compounds. 

986. Some plants produce in considerable quantities a sub- 
stance resembling beeswax, which has the same chemical constit- 
uents as the fats and oils. The glossy coating or varnish which is 
observed on the surface of leaves, fruit, and bark, rendering them 
impermeable to water, consists of vegetable wax. 

987. Beeswax, a secretion of the honey bee, is the most im- 
portant of these bodies. In its ordinary state it is yellow, but is 
bleached white by exposing it for some time in thin ribands to the 
joint action of air, light, and moisture. "Wax is principally used 
in the manufacture of candles. 

988. Resins are supposed to be formed by the oxidation of the 
essential oils. They are found in most plants, and exude from 
many of them in the form of a more or less viscid liquid, which 
consists of the resin united with a portion of essential oil. The 
pure resins are translucent, brittle solids, insoluble in water, but 
soluble in alcohol, ether, and volatile oils. They are good con- 
ductors of electricity, are highly inflammable, and burn with a 
smoky flame. They are of various colors, but generally brown, 
green, or red. 

989. Common Pine Resin — Colophony — Rosin. — This is the 
residue left after the distillation of crude turpentine, and constitutes 
from 75 to 90 per cent, of its weight. Common rosin consists of 
two isomeric acids, the syfoic and pinic, which unite with bases to 
form salts, and with alkalies to produce soaps. An oil termed 
sylvic, or rosin oil, is obtained from this variety by distillation. It 
is used for illuminating purposes, and for lubricating machinery. 
Eosin is also employed to increase friction by rubbing it on the 
belts of machinery and various other surfaces, as it renders them 
rough and adhesive. 

990. Lac is a resinous substance of much importance, found 
as an exudation on the branches of various trees in tropical coun- 

of the third class? 986. Describe vegetable wax. 987. What of beeswax? 
988. What are resins, and where found? Their properties? 989. What is com- 
mon rosin, and of what does it consist? Mention the uses of rosin oil and of 
rosin ? 990. What is lac, and how formed ? What is stick lac ? Seed lac ? Uses ? 



RESINOUS AND WAXY COMPOUNDS. 357 

tries. The bark is punctured by an insect, thus opening a passage 
for the juice which, as it flows out, hardens over the insects. The 
twigs, when removed in this condition, constitute the stick lac of 
commerce. The resinous mass, when digested in a solution of 
carbonate of soda, yields a red coloring matter contained in the 
insects. This is largely used as a dye in the place of cochineal. 
The portion insoluble in the carbonate of soda is called seed lac, 
and this, when melted and purified, is shell lac. Lac is exten- 
sively consumed in the manufacture of varnishes and sealing wax, 
and also as a stiffening for hats. Guaiacum is a resin of a dark, 
greenish-brown color, and is the product of the lignum vitse tree. 
It is used medicinally. 

991. Gum Resins are the solified milky exudations of plants. 
They consist of resin, essential oils, and a gummy substance pecu- 
liar to the plant. They are soluble in rectified alcohol, and form 
a class of valuable medicinal agents. Ammoniacum, assafoztida, 
aloes, myrrh, gamboge, &c, belong to this class. 

992. Balsams. — This name is given to the fluid compounds of 
resin and essential oil that exude from trees and shrubs. Among 
the most important are turpentine, balsam copaiba, balsam tolu, 
and gum benzoin. From the latter is obtained benzoic acid. 

993. Amber is a fossil substance, sometimes occurring in 
beds of coal, but usually found on the shores of the Baltic Sea, 
where it is washed up by the waves during long storms. It is a 
mixture of several resinous •substances, and often incloses insects 
in a state of beautiful preservation ; hence it is supposed to be a 
solidified resin. It is a yellowish, translucent body, somewhat 
heavier than water, and has the property of becoming electric by 
friction. Being quite hard and susceptible of a fine polish, it is 
used for making ornaments. 

994. Varnishes are solutions of various resins in alcohol, the 
essential oils, or the drying oils, and are employed to give lustre 
and hardness to exposed surfaces. When alcohol is the solvent, 
the product is a spirit varnish ; when oil is used, an oil tarnish. 
The resins principally used in the manufacture of varnish are mas- 
tic, sandarac, copal, lac, &c. 

995. Elastic Gums — Caoutchouc or India Rubber. — This is 

What is guaiacum ? 991. Describe gum resins. Examples. 992. What of bal- 
sams? 993. What is amber, and where found? State its properties and use. 
994. What of varnishes ? 995. What is caoutchouc, and how obtained ? Give its 



358 ORGANIC CHEMISTRY. 

the product of several tropical trees, from which it exudes as a 
yellowish, milky liquid, in which the small caoutchouc globules are 
mechanically suspended. The juice is spread out in films, when it 
rapidly dries away, leaving the caoutchouc as a thin, elastic layer 
of a brownish-yellow color. Or, the juice is collected in vessels 
and poured in successive layers over moulds, on which it is dried 
by artificial heat. Pure caoutchouc is nearly white, the ordinary 
black color of the gum being due to the smoke which arises from 
the fire during the drying process. The solvents of caoutchouc 
are pure ether, chloroform, bisulphide of carbon, coal naphtha, 
and rectified oil of turpentine. It melts at about 250°, but on 
cooling does not return to its solid state. Caoutchouc contracts 
on being heated, thus forming one of the exceptions to the gen- 
eral law of expansion by heat (251), 

996. Vulcanized India Rubber is formed by charging caout- 
chouc with two or three per cent, of sulphur. The operation in- 
creases its elasticity, and also its capacity for retaining it both at 
high and low temperatures. It moreover increases its insolubility, 
and fits it for a thousand applications in the arts for which ordinary 
caoutchouc would be unsuitable. The addition of magnesia and 
some bituminous matter to vulcanized rubber, gives it a high de- 
dree of hardness, and renders it susceptible 

Fig. 275. f a fine polish, but in a great measure de- 

stroys its elasticity. In this state it is 
largely used in the manufacture of combs, 
knife handles, and various ornamental ar- 
ticles. Caoutchouc, from the cohesiveness 
of its freshly cut edges, its elasticity, 
pliancy, and power of resisting most chem- 
ical agents, is of great use in the laboratory. 

Cohesion 'of Caoutchouc. If a P iece of slieet rubber be trapped over 

a glass rod, Fig. 275, on pressing together 
its freshly cut edges with a gentle heat, they will unite, forming a 
flexible tube which, on being tightly tied over two glass tubes, will 
serve to connect them together gas-tight. 

997. Gutta Percha is a substance resembling caoutchouc, and 

properties. Its solvents. To what is it an exception ? 996. How is vulcanized india 
rubber made? What is the change effected? How is it rendered still harder? 
For what used ? Why is caoutchouc useful to the chemist ? Describe Fig. 275. 
997. What is gutta percha, and how obtained ? Give its properties. Its uses. 998. 




ACTION OF ALKALIES UPON OILS — SOAP. 359 

obtained from plants in the same form of milky exudation. Under 
ordinary circumstances it is a tough, hard, unelastic body, insolu- 
ble in water or alcohol, but soluble in chloroform, bisulphide of 
carbon, turpentine, and most of the essential oils. Immersed in 
warm water, it becomes soft and plastic, and admits of being 
moulded in any desired form, retaining its shape on being cooled. 
In consequence of this property it is used in taking casts and impres- 
sions, copying the finest lines with fidelity. It is also readily welded 
while in this waxy condition. It is of a pale brown color, is an 
insulator of electricity, and becomes negatively electric by friction. 

§ VI. Action of Alkalies upon Oils — Soap. 

998. Saponification. — It was stated that the oils and fats are 
saline bodies, consisting of fatty acids combined with a common 
base, glycerin. TThen other bases, as potash, soda or ammonia, 
are made to act upon the fatty substances, they expel the glycerin 
and take its place, uniting with the acids and forming soap. Soaps 
are therefore regular salts ; combinations of margaric, stearic and 
oleic acids with potash, soda, ammonia, or lime. The change by 
which they are produced is called saponification. 

999. Process of Soap Making. — The alkalies generally used 
for soap making are potash and soda, They require to be in a 
caustic state, which is produced by dissolving them and passing 
the solution (lye) through newly slacked lime, which takes away 
the carbonic acid. In this caustic ]ve 1 the fats are boiled, their 
glycerin set free, and the soap formed in a state of solution in the 
water. To obtain it in a solid form the solution is boiled down till 
the soap ceases to be soluble and rises to the surface, when it is 
drawn off into moulds. Soda soap may be separated from the wa- 
ter in which it is dissolved by adding common salt, which forms 
a brine and at once coagulates the soap ; if potash lye is used, the 
addition of salt decomposes the potash soap, forming a soda soap, 
and chloride of potassium. 

1000. Hard and Soft Soaps. — The consistence of soap depends 
chiefly upon its alkali. Hard soaps are made of soda, or a mix- 
ture of soda and potash, while in soft soaps potash alone is used, 

How is soap produced ? VThat is saponification ? 999. Name the alkalies used. 
Describe soap making. How may soap be separated from the water ? 1000. How 
do hard and soft soaps differ? 1001. What is castile soap? CoGoa soap. 



360 ORGANIC CHEMISTRY. 

the latter alkali being deliquescent and consequently attracting 
water, which renders the soap liquid. The consistence of the oil 
or fat also influences the quality of hardness. Those containing a 
large proportion of stearin and margarin, like tallow, form hard 
soaps, while those in which olein predominates, as the soft fats and 
oils, produce soft soap. The glycerin which is retained in soft 
soap also adds to its fluidity. 

1001. Castile Soap is composed of olive oil and soda, its 
mottled appearance being due to the oxide of iron, with which it 
is colored. Soap made with cocoanut oil has the property of dis- 
solving in salt water, and is therefore used at sea. 

1002. Properties.— Soap has a powerful affinity for water and 
may retain from 50 to 60 per cent, of it and still continue solid ; 
hence dealers generally keep it in damp places where it will ab- 
sorb moisture. It is soluble in fresh water, but with the excep- 
tion of cocoa soap, is insoluble in salt water. Soap dissolved in 
spirits of camphor, forms opedildoc. Volatile liniment is an am- 
moniacal soap. 

1003. Mode in which Soap acts in Cleansing. — As water, 
having no affinity for oily substances, will not dissolve them, of 
course it cannot alone remove them from surfaces to which they 
may adhere. The oily matters which are constantly exuding from 
the glands of the skin, uniting with the outer dust, form a film 
over the body. The alkali of the soap acts upon the oil during 
ablution, partially saponifies it, and renders the unctuous compound 
freely miscible with water, so as to be easily removed. The cuti- 
cle or outer layer of the skin is chiefly composed of albumen, 
which is soluble in the alkalies. The alkali of the soap, therefore, 
dissolves off a portion of the cuticle with the dirt ; every washing 
with soap thus removing the old face of the scarf-skin and leaving 
a new one in its place. The action of soap in cleansing textile 
fabrics is of a similar nature. Alkalies not only act upon greasy 
matter, but as is well known, dissolve all organic substances. In 
the case of soap, however, the solvent power of the alkali is in 
part neutralized, thus preserving both the texture and color of the 
fabric exposed to its action. The oily nature of the soap also in- 
creases the pliancy of the articles with which it is washed. 

1002. What of soap in relation to water ? What is opedildoc ? Volatile liniment ? 

1003. How does soap act in cleansing? Explain its action upon the skin. Upon 
textile fabrics. 1004. What of washing fluids ? Of camphene ? 1005. Where and in 



VEGETABLE ACIDS. 



361 



1004. Solutions of the alkalies under the name of washing 
fluids are often used in cleansing textile fabrics. They act by 
precipitating whatever earthy salts the water may contain, there- 
by rendering it soft, and supplying an excess of alkali. Cam- 
phene, which has the property of dissolving oily substances 
without injuring the fabric, is sometimes employed as a detergent. 



CHAPTER XXI. 



Fig. 276. 



ORGANIC ACIDS, BASES, AND COLORING PRINCIPLES. 

§ I. Vegetable Acids. 

1005. These substances are numerous in the vegetable king- 
dom, occurring abundantly in fruits, and often in the leaves, bark, 
and roots of plants. They exist in a 
free state, and combined with bases, 
forming acid and neutral salts, both 
soluble and insoluble. They sometimes 
accumulate in the cells of plants in the 
form of crystals, of which Fig. 276 is an 
example from the cells of an onion. 

1006. They usually consist of car- 
bon, hydrogen, and oxygen, the latter 
element being greatly in excess. Ox- 
alic acid, however, contains only carbon 
and oxygen, and in acetic acid the hydrogen and oxygen are in 
the proportion to form water. Some of these acids have been de- 
scribed in connection with groups to which they naturally belong, 
while the mode of their production is treated in Physiological 
Chemistry. "We shall consider here a few others of the most im- 
portant. 

1007. Tartaric Acid, C 8 H 4 O 10 , 2H0.— This acid is found 
abundantly in grapes, and is also present in the tamarind, the 
unripe berries of the mountain ash, and in small quantity in other 
plants. It exists in grape juice as bitartrate of potash (cream of 




Cn-stals in Cells. 



what state are organic acids found ? Of what is Fig. 276 an example ? 1006. What 
is said of their composition ? 1007. Where is tartaric acid found, and how ob- 
16 



362 ORGANIC CHEMISTRY. 

tartar), and is gradually deposited in the form of a hard crust on 
the sides of vessels in which wine is kept. From this bitartrate, 
it is obtained by the action of chalk and sulphuric acid. Its crys- 
tals, when pure, are colorless, transparent, permanent in the air, 
and dissolve readily in water or alcohol. It is extensively used 
by the calico printer and dyer for the removal of mordants. 
Mixed with bicarbonates of the alkalies, it forms the soda pow- 
ders of the effervescing draughts. 

1008. Rochelle Salt is a tartrate of potash and soda, produced 
by saturating a solution of cream of tartar with soda. Tartar 
emetic, or tartrate of antimony and potash, long used medicinally, 
is a violent emetic and cathartic poison. 

1009. Citric Acid, doHsOn^HO, is found principally in 
fruits of the orange family (Aurantiacte), but is of frequent occur- 
rence in gooseberries, currants, and other acid fruits. It may be 
readily procured from the juice of the lemon by the aid of chalk 
and sulphuric acid. It has a pleasant acid taste, is very soluble 
in water, and is used in medicine, calico printing, and for effer- 
vescing draughts. 

1010. Malic Acid, 8 II 4 O 3 , 2H0, is the principal acid of un- 
ripe apples, hence its name from malus, apple. It is found abun- 
dantly in most acid fruits, and in the stalks of rhubarb, but is 
usually obtained from the unripe berries of the mountain ash. It 
is a colorless solid, dissolves readily in water and alcohol, and 
crystallizes with difficulty. The solutions of all the acids named 
have an agreeable acid taste, but become mouldy if long kept, and 
gradually undergo decomposition. 

1011. Oxalic Acid, 2 3 ,HO. — This substance imparts the 
acid taste to common sorrel and the rhubarb plant, in which it 
exists as binoxalate of potash. In the barilla plant it is found as 
oxalate of soda, and in many lichens as oxalate of lime. It is 
commonly prepared by the oxidation of sugar or starch with 
nitric acid : 1 part of sugar is dissolved in 8 parts of nitric acid, 
and gently heated, when intense action ensues, with a copious 
disengagement of nitrous acid fumes. The crystals obtained are 
intensely sour and poisonous, and resemble Epsom salts, for 
which they are sometimes mistaken. In cases of poisoning with 

tained? State its appearance and uses. 1008. What is Rochelle salt? Tartar 
emetic? 1009. Give the origin and properties of citric acid. 1010. Of malic. 
1011. Give the composition of oxalic acid. Where is it found, and how procured? 



VEGETABLE ACIDS. 363 

it, chalk or magnesia, suspended in water, is the proper anti- 
dote. 

1012. Oxalic acid is largely nsed in calico printing, and it is 
also employed as a delicate test for the presence of lime, with 
which it forms an insoluble salt. It removes ink and iron stains 
from linen by forming a soluble oxalate of iron, but the acid is so cor- 
rosive as to injure the fibre if not immediately removed by washing. 

1013. Tannic Acid, 54 H2 2 34 . — There are several distinct 
compounds known under the name tannin, w^hich resemble each 
other in character and possess an acid reaction. They are found 
extensively diffused throughout the vegetable kingdom, and are all 
distinguished by an astringent taste. The bark and leaves of most 
forest trees, as well as of many fruit trees, contain a large quan- 
tity of tannin, and it is also found in various roots, shrubs, and 
seeds. Tannin is the astringent principle of tea and coffee. 

1014. The most important of these compounds is that obtained 
from gall nuts — the gallotannic acid. It has an intensely astrin- 
gent taste, reddens litmus paper, and is very soluble in water. 
Tannic acid combines with the salts of the peroxide of iron, form- 
ing a blue-black precipitate used for coloring, and also in the man- 
ufacture of writing ink. The gradual darkening of pale watery 
ink is due to the oxidation of the iron it contains. Tannin forms 
insoluble compounds with starch, gelatin, and other organic bodies, 
the most remarkable being that with gelatin, w^hich is the basis of 
leather. 

1015. Gallic Acid is found associated with tannin in the gall 
nut, sumach, and other vegetable bodies, and is formed from tan- 
nic acid by exposing a solution of it for some time to the air. It 
crystallizes in silky needles, is freely soluble in boiling water, and 
does not precipitate gelatin. On applying a regulated sand heat, 
gallic acid is decomposed and pyrogallic acid obtained. This 
acid is extensively used in photography. Both pyrogallic and 
gallic acids decompose the salts of silver, gold, and platinum; a 
property which is utilized in coloring human hair. The hair is 
first wet with a solution of gallic acid, and after drying, is moist- 
ened with an ammoniacal solution of a salt of silver. The salt is 

What of its crystals and the antidote ? 1012. What is said of its uses ? 1013. Where 
are the compounds of tannin found ? 1014. What is the most important? Give 
its properties. Uses. To what is the darkening of ink due ? What compounds 
does tannin form ? 1015. How is gallic acid obtained ? Pyrogallic ? For what 



364 ORGANIC CHEMISTRY. 

decomposed and the liberated metal dyes the hair of a fine and 
permanent black or brown. 

1016. There are many other vegetable acids yet imperfectly 
known, and many more the results of natural and artificial decom- 
position; but tkey are not of sufficient importance to be here 
noticed. 

§ II. The Organic Bases. 

1017. The Vegetable Alkaloids or Organic Bases are an im- 
portant natural group of substances, chiefly formed in vegetables 
and giving to them their active properties. They are always found 
in the form of salts, and usually in combination with an organic 
acid. Nitrogen is an invariable element of the alkaloids, but some 
of them contain no oxygen. Those destitute of oxygen are oily, 
volatile bodies obtained by distillation, and as they absorb oxygen 
rapidly from the air, they are produced in a current of hydrogen, 
or carbonic acid. Those which contain oxygen are prepared by 
dissolving the vegetable matter in dilute chlorohydric or sulphuric 
acid, which forms a soluble salt with the alkaloid. To the filtered 
solution a stronger base is added — such as lime, ammonia, or mag- 
nesia, which produces a copious precipitation of the alkaloid. 

1018. Properties. — These bodies dissolve sparingly in water, 
but freely in boiling alcohol, are intensely bitter, and usually re- 
store the reddened color of litmus. They are the most powerful 
medicines and poisons known. Gallotannic acid precipitates most 
of the organic bases, forming insoluble compounds ; hence it is an 
excellent antidote to them when they have been taken in poison- 
ous doses. "We shall notice only the more important alkaloids 
found in vegetable substances. 

1019. Quinia, O 40 H 24 N 2 O 4 + 6Aq. — Quinine is extracted 
from pulverized Peruvian bark by acidulated water. It is a white, 
crystalline substance, which unites with acids, producing intensely 
bitter salts. The sulphate of quinine, which forms light, bulky 
crystals, is the salt employed in medicine. It dissolves sparingly 
in water, but freely in dilute sulphuric acid and alcohol. Cincho- 
nine is an analogous alkaloid from the same source. 

are tliey used ? How do they color the hair ? 1017. What is said of the organic 
bases! What of those destitute of oxygen? How are those containing oxygen 
prepared? 1018. Mention the properties of these bodies. What is the effect 
on them of gallotannic acid ? 1019. Give the origin and properties of quinia. 



THE ORGANIC BASES. 365 

1020. Nicotine, C^H^Nx, a volatile alkaloid, is the active 
principle of the tobacco plant. It is a colorless, inflammable, oily 
liquid, with a powerful and irritating odor of tobacco. It is 
contained in the smoke of the burning leaves and is exceedingly 
poisonous, a single drop being sufficient to kill a large dog. 

1021. Morphia, C 34 H 19 N0 6 -f 2Aq. — Morphine is the active 
principle of opium, which is the hardened, milky juice of the 
poppy. Opium is a very complex body, containing no less than 
seven organic bases and several other well-defined principles. 
Morphine (from Morpheus, in consequence of its sleep-inducing 
property) is a crystallizable, resin-like body, without odor, and 
possessing a bitter, disagreeable taste. It is a powerful narcotic 
and poison, largely used in medicine. 

1022. Strychnia, C A2 K 22 S 2 0±.— Strychnine is chiefly ob- 
tained from the beans of the strychnos nux vomica, a small East 
Indian tree, but is found in several other plants belonging to that 
tribe. Cold water dissolves only -^^ of its weight of strychnine, 
but it is soluble in essential oils and chloroform. Such is its in- 
tense bitterness that it imparts it perceptibly to 700,000 times its 
weight of water. It is a deadly poison, ^ of a grain killing a dog 
in 30 seconds. It takes effect upon the nerve centres of the spinal 
axis, producing fearful convulsions. The terrible woorara poison, 
with which the South American natives poison their arrows, and 
which has been lately used as a remedy for tetanus, is a variety of 
strychnine. So also is the poison of the upas tree of Java- 
Brucia is an alkaloid closely allied to strychnine and obtained 
from the same genus of plants. 

1023. Common lettuce has slight narcotic properties, which 
are due to an alkaloid, lactucine. In the same way conicine is ex- 
tracted from the hemlock; aconitine, or aconite, from the monk's 
hood; solanine from potato sprouts ; piperine from black pepper, 
and emetine from ipecacuanha. 

1024. Caffeine or Theine, C 16 H 10 N 4 O 4 4-2 Aq.— The active 
principle of coffee, caffeine, and of tea, theine, as also of the mate 
or Paraguay tea, are identical in composition. It is interesting 
to observe that the plants which have been selected to furnish 

1020. What of nicotine? 1021. Describe morphia. Its properties. 1022. Where 
is strychnia found ? State its properties. What of the woorara and upas poisons ? 
What is brucia ? 1023. Mention some other vegetable alkaloids. 1024. Give the 
composition of theine. What is an interesting fact regarding this principle ? State 



366 ORGANIC CHEMISTRY. 

infusions for the daily beverage of three fourths of the human race 
should contain one and the same nitrogenized principle. Theo- 
bromine, the active constituent of chocolate, is also nearly allied to 
caffeine. Coffee seldom contains more than one per cent, of the 
principle, while tea furnishes three or four. Caffeine crystallizes 
in long, flexible, silky needles, has a slightly bitter taste, and dis- 
solves sparingly in cold water, but freely in hot water. 

1025. Tea consists of four principal constituents. First, a 
yellow volatile oil, which produces its peculiar aromatic odor and 
flavor. It does not exist in the natural leaves, but is produced by 
the roasting process to which they are subjected. Tea yields but 
1 per cent, of this oil. Second, theine. Third, tannic acid, which 
forms from 12 to 18 per cent, of its weight, and gives to tea its 
astringent properties. Fourth, tea leaves contain some 15 per cent, 
of an insoluble, glutinous substance, which is lost with the ' grounds.' 

1026. The varieties of tea are numerous, depending upon soil, 
climate, time of picking the leaves, and the modes of their prepara- 
tion. Green tea is prepared from the young leaves, which are 
roasted and withered almost immediately after they have been 
gathered. They are then rolled in the hand, by which they ac- 
quire their twisted appearance, and quickly dried, sifted, and win- 
nowed ; the whole operation being brief and simple. Black tea, 
on the contrary, upon being gathered, is exposed to the air for ten 
or twelve hours. It is then roasted, a large quantity of liquid ex- 
pressed from it, and after several alternate rollings, roastings, and 
exposures to the air, it is slowly dried over a charcoal fire. The 
dark color of black teas is mainly owing to the action of oxygen 
upon the juices during the long exposure of the leaves. 

1027. Constituents of Coffee. — Besides its caffeine, the coffee 
berries contain a considerable proportion of gluten, 5 per cent, of 
caffeic acid, and 14 or 15 per cent, of a fixed oil. An aromatic 
flavoring oil is developed during roasting, but according to Payen 
it does not exceed the ^Vo P ar ^ °f the weight of coffee. 

§111. Organic Coloring Principles. 

1028. As a class, vegetable coloring matters do not possess 
many chemical characters in common, and are associated together 

its proportion in tea and coffee. Its properties. 1025. Of what does tea consist ? 
1026. What occasions the varieties of tea ? How is green tea prepared ? Black 
tea ? To what is its dark color owing ? 1027. What are the constituents of coffee ? 



ORGANIC COLORING PRINCIPLES. 



367 



on account of their common applications in the arts. Some are 
acid, others neutral; some ternary, others quaternary. The 
most brilliant of vegetable colors, those of flowers, are fugitive, 
small in quantity, and difficult to separate. The coloring matters 
in the interior of plants, where they are not exposed to light, are 
less brilliant, but more durable. The coloring matters of plants 
are chiefly blue, yellow, and red ; no genuine black having been 
obtained from them. 

1029. Dyeing. — The art of the dyer consists in impregnating 
textile fabrics with the various coloring matters in such a way 
that they will remain permanent, or fast, under wear and wash- 
ing. Some coloring substances, as indigo for example, unite di- 
rectly with the fibres, producing fixed or substantive colors. 
Others, those chiefly which are soluble in water, do not adhere ; 
they therefore require some intermediate substance which has an 
affinity for both the coloring matter and the fibre, and will bind 
them together in an insoluble compound. Such a substance is 
called a mordant, from the latin mordeo, to bite, because it was 
supposed to bite in the colors. Dyes which require a mordant 
are called adjective colors, and nearly all vegetable colors are of 
this kind. 

1030. The principal mordants are salts of tin, iron, and alumi- 

Fig. 277. Fig. 278. 





Cotton Fibres. 



Linen Fibres. 



Woollen Fibres. 

na, which not only fasten the colors, but so change them that one 
dye stuff" gives different colors with different mordants. The tex- 

1028. What is said of the permanence of vegetable colors ? 1029. In what does 
dyeing consist ? What are substantive colors ? Mordants ? Adjective colors ? 
1030. Wbat of the principal mordants? 1031. Describe the process of calico 



368 OKGANIC CHEMISTRY. 

tile fibres consist of hollow tubes, Figs. 277 and 278, which the 
mordant is supposed to enter, filling them like lungs, and thus 
facilitating the chemical action. 

1031. Calico Printing. — In this operation the bleached and pre- 
pared goods are printed with the mordants by patterns upon blocks 
or cylinders. As the cloth is subsequently passed through the dye, 
the coloring matter is fixed upon those parts where the mordant 
was applied. When the fabric is afterward washed, the color 
disappears from the other portions of the goods, and the printed 
figure appears. 

1032. Blue Coloring Matters. — Indigo is obtained from the 
juices of a large number of East India and American plants, the prin- 
cipal of which belong to the genus indigofera. This juice is color- 
less, but when exposed to the air it absorbs oxygen, and deposits a 
blue sediment which, in the form of a powder or cakes, is known as 
commercial indigo. It is nearly insoluble in all liquids except sul- 
phuric acid, with which it combines, forming sulphindigotic acid. 
When deoxidized, indigo becomes colorless and soluble in water, 
but on exposure to the air it again absorbs oxygen, and acquires 
insolubility and its deep blue color. Fabrics may therefore be 
steeped in a solution of colorless indigo, and on exposure to the air 
acquire a bright and permanent blue tint. If goods are boiled in 
sulphindigotic acid, a still brighter color (Saxon blue) is produced. 

1033. Litmus is obtained from several species of lichens, 
which are destitute of color. The product is at first purple, or 
red, but is changed to blue by the action of the ammonia used in 
its preparation. 

1034. Red Coloring Matters. — Madder.— The roots of the 
madder plant, ground to powder, furnish this valuable dye stuff. 
It is at first yellow, but reddens by exposure to air and ab- 
sorption of oxygen. In addition to red, madder furnishes purple, 
yellow, orange, and brown. Brazil wood and sandal wood pro- 
duce red coloring matters, and the flowers of the red saffron yield 
safflower. Carmine is contained in a species of Mexican cactus, and 
is obtained from the cochineal, an insect which feeds upon that 
plant. It affords a brilliant red and purple dye. 

1035. Yellow Coloring Matters. — Among the principal of 



printing. 1032. How is indigo obtained ? What is sulphindigotic acid ? Explain 
the action of indigo upon fabrics. 1033. What of litmus ? 1034. What is madder ? 
Mention other red dyes. 1035. What are the principal yellow dyes ? 1036. What 




Chlorophyll in Cells. 



ORGANIC COLORING PRINCIPLES. 369 

these are quercitron, from the bark of the black oak ; fustic, from 
the wood of the West Indian mulberry, and weld, from the reseda 
luteola. Annotto, nsed in dyeing nankeen, and also to color butter 
and cheese, is extracted from certain seeds grown in South 
America. Turmeric is obtained from the roots of an East Indian 
plant. 

1036. Chlorophyll {Leaf-green) is the substance to which 

the vegetable world owes its uniform green color. It is of a 

resinous nature, soluble in alcohol and acids, but insoluble in 

water. Fig. 279 shows the 

Fig. 279. 
grains of chlorophyll and 

needle-like crystals in the cells 
of a leaf. It exists only in 
minute quantity in plants, the 
leaves of a large tree, according 
to Berzelitts, containing per- 
haps not more than 100 grains. 
This substance appears to be a direct product of the action of the 
sunbeam upon vegetation, as it is never seen except in those parts 
exposed to the light. Plants removed from a dark cellar into 
the sunlight turn rapidly of a green color, and every one may 
have remarked in spring how quickly, after a few days of cloudy 
weather, the unfolding vegetation is changed to a deep green by 
the rays of the sun. The change from green to red and yellow in 
the autumn leaves, is supposed to be owing to the oxidation of 
their chlorophyll. 

1037. Extractive Matter. — This term has been applied to nu- 
merous substances, chiefly vegetable, extracted by chemists, which 
have not yet been accurately examined. The number of known 
plants exceeds a hundred thousand, and each possesses peculiar 
principles in small quantity to which its flavor and medicinal 
properties are due. Of this vast number, but few comparatively 
have been studied by chemists, who designate whatever of this kind 
that is unknown as extractive matter. 



is chlorophyll ? Why is it thought to be a direct product of the sunbeam ? What 
of the change in autumn leaves? 1037. What does the term extractive matter 



16* 



370 ORGANIC CHEMISTRY. 

CHAPTER XXII. 

NITROGENOUS COMPOUNDS-THEIR CHANGES AND EFFECTS. 

§ I. The Albuminous Compounds. 

1038. The substances now to be noticed differ in very im- 
portant respects from those hitherto considered. They have more 
elements ; they contain nitrogen in higher proportions, have a 
larger number of atoms, and are therefore more complex and 
prone to change. They do not crystallize, and are highly organ- 
ized. Though originating in the vegetable kingdom, they furnish 
the basis of the structures of all animal systems. The group 
comprises albumen, fibrin, casein, and their several modifications, 
and is hence called the albuminous or albuminoid group. 

1039. Albumen. — "We are most familiar with this body in the 
form of white of eggs, a glairy, insipid fluid, which coagulates by heat, 
producing a white solid ; hence its name, from albus, white. Albumen 
forms about 7 per cent, of the blood, and is found in variable pro- 
portions in all the secretions of the body. It also exists dissolved in 
the juices of plants, or dried in their seeds. When the water which 
has been used to wash starch from wheat flour or scraped potatoes, 
is allowed to stand until it becomes clear, and is then boiled, it 
assumes a turbid appearance, and deposits a flaky-white substance, 
which has the same character as white of egg, and is known as 
vegetable albumen. When dried it forms a brittle, yellow, gummy 
mass, which dissolves in cold water ; but when coagulated it will 
not dissolve in water, either cold or hot. The change of coagula- 
tion does not alter its composition. The temperature at which it 
takes place varies ; a strong solution of albumen in water becomes 
completely insoluble at 145°, and separates in flakes at 167°. 
The more it is diluted with water, the higher the temperature of 
coagulation. 

1040. Chemical Properties. — Albumen consists of carbon, 
oxygen, hydrogen, and nitrogen — some 16 per cent, of the latter — 
and a small but definite proportion of sulphur and phosphorus. 

signify ? 1038. How do the nitrogenous compounds differ from those hitherto 
considered ? What does the albuminous group comprise ? 1039. What is the 
most familiar form of albumen? Where is it found? What is vegetable albu- 
men ? Its properties ? 1040. Give the composition of albumen. For what is it an 



THE ALBUMINOUS COMPOUNDS. 371 

Its exact composition, however, is not determined. It is coagu- 
lated by many substances, as alcohol, strong acids, creosote, and 
corrosive sublimate ; therefore, in poisoning by these bodies, if the 
white of eggs be promptly swallowed, it seizes upon the noxious 
compounds and protects the stomach. Albumen, like water, seems 
capable of combining with both acids and bases. Alkalies render 
it soluble. White of egg and blood are both slightly alkaline, from 
the presence of soda; the albumen being supposed to exist as al- 
buminate of soda. It forms also definite compounds with the acids. 
Vitellin is the albumen of the yolk of eggs. 

1041. Fibrin is the name given to the substance which forms 
the basis or fibre of muscular tissue. It occurs in bundles, as 
shown in Fig. 280, the parallel 

fibres having wrinkles or cross 
markings. If a piece of lean 

beef be long washed in clean f^^J|^^|3^^^§ IlliK^ 
water, its red color, which is 
due to blood, gradually disap- 
pears, and a mass of. white, fi- ^^^^ffi^©^fe 
brous tissue remains which is 

. . Fibres of lean Meat, magnified. 

known as animal fibrin. Like 

albumen, it is capable of existing in two states : the soluble and 
the insoluble. In its soluble form it is a constituent of blood, 
forming in the healthy state about 2 parts in 1000 parts of that 
liquid. The clotting of blood, when freshly drawn, is due to the 
coagulation of its fibrin, which solidifies into a network of fibres. 
Dilute solutions of potash and soda dissolve fibrin, as they do al- 
bumen. 

1042. Gluten — Vegetable Fibrin. — When wheat flour is made 
into a dough and then kneaded on a sieve or piece of muslin under 
a stream of water, its starch is washed away and there remains a 
gray, tough, elastic substance, almost resembling animal skin in 
appearance. When dried it has a glue-like aspect, and is there- 
fore called gluten. The crude gluten thus prepared, when freed 
from oil, albumen, &c, proves to be identical in composition with 
animal fibrin, and is hence named vegetable fibrin. Like muscle 
fibrin, it is soluble in very dilute chlorohydric acid. 

antidote ? Its chemical properties ? 1041. Describe animal fibrin. What is its rela- 
tion to blood? 1042. How may gluten be procured? Why is it called vegetable 




372 OEGANIC CHEMISTRY. 

1043. Casein is an essential constituent of milk, existing in it 
to the extent of about 3 per cent., and forming its curd, or cheesy 
principle. Its soluble form in milk is due to a small portion of 
free alkali, and when this is neutralized by an acid, the casein is 
precipitated, or the milk curdles. By neutralizing the acid, the 
casein is re-dissolved. The water in which flour has been washed 
contains a small portion of a substance, which is coagulated by 
acids ; it resembles the curd of milk, and is called vegetable casein. 
It is found in large proportion in peas and beans. The Chinese 
make a cheese from peas which gradually acquires the smell and 
taste of milk cheese. 

1044. Chemical Composition. — There is a remarkable identity 
in composition among the members of this group. The analysis 
of albumen from the hen's egg gives carbon 53.5, hydrogen 7, 
nitrogen 15.5, oxygen 22, sulphur 1.6, phosphorus 0.4; and, with 
slight variations in the proportions of sulphur and phosphorus, 
this may represent the composition of the whole group. Liebig 
gives the following formula as the best approximation yet obtain- 
ed toward their composition : 



Albumen of blood, ) 

Albumen of flesh, V C 2 i 6 H 169 68 N 27 S 2 

Fibrin of flesh, ) 

Albumen of eggs, C 2 i 6 H, 69 68 N 27 S 3 

Casein, C 288 H 228 O 90 N 3C S 2 

Fibrin of blood, C 298 H 228 92 "N 40 S 2 



An important fact concerning these compounds is that they 
are physiologically isomeric— are convertible into each other in 
the animal system. 

1045. Protein. — When these albuminoids are dissolved in a 
solution of potash or soda by a gentle heat, if an acid be added, a 
grayish precipitate is formed, which is attended with the libera- 
tion of sulphur and phosphorus in the form of sulphuretted hy- 
drogen and phosphoric acid. Mulder calls this substance protein, 
and he and many other chemists regard it as the radicle or base 
of the whole group. They hold it to contain neither sulphur nor 
phosphorus, and suppose the different albuminous bodies to be 
formed by combinations of protein with these elements and oxygen. 
Liebig and his adherents deny that any such radicle has ever been 
freed from sulphur, and reject the doctrine of protein altogether. 

fibrin ? 1043. Describe casein. What occasions the curdling of milk ? What of 
vegetable casein? 1044, What is said of the composition of the albuminoids? 






PUTEEF ACTION AND DISINFECTION. 373 

1046. These substances will be noticed in their physiological 
relations when we consider the subject of animal nutrition. The 
remarkable advance in organic chemistry of late years has brought 
them forward into new relations, and they have received many 
names. They are called protein compounds, nitrogenous aliment- 
ary principles, and as one of the names of nitrogen is azote, they 
are termed azotized substances. As they form the materials from 
which the body is nourished and built up, Liebig named them the 
plastic elements of nutrition ; they are also known as flesh-forming 
and Hood-producing compounds. 

§11. Putrefaction and Disinfection. 

1047. A leading characteristic of the foregoing substances is, 
as we have stated, their instability. This is due, first, to the 
presence in large proportion of the fickle element nitrogen ; sec- 
ond, to the large number of elements combined together, and the 
resulting complexity of the attractions ; and third, to the great 
number of atoms associated, or the massiveness of the molecules. 
"When in a moist state, and exposed to atmospheric oxygen, the 
tottering equilibrium of the chemical fabric is overturned, and out 
of its ruins a new class of substances is produced. It is well 
known that flesh, blood, milk, dough, &c., all of which are rich 
in nitrogenous substances, will preserve their properties in the air 
only a short time, and pass into a state of decomposition, giv- 
ing forth offensive exhalations. This change is called putrefac- 
tion, and when once commenced, it rapidly spreads through the 
mass, communicating itself to all putrifiable substances with which 
it is brought in contact. 

1048. Propagation of the Effects.— As a spark may kindle a 
conflagration that shall consume a city, so the minutest amount of 
putrescent matter is sufficient to affect an indefinite quantity of 
changeable substance. The remarkable communicability of these 
effects and their potency of action are painfully illustrated by phy- 
sicians, who sometimes wound themselves while dissecting. The 
small trace of decomposing matter from the dead body which 
clings to the dissecting knife is sufficient to establish a rapid de- 

1045. Give the origin of protein. How is it considered by different chemists? 
1016. By what names are the albuminoids known ? 1047. What is a leading prop- 
erty of these substances ? To what is it due ? "What is putrefaction ? 1048. What 



374 ORGANIC CHEMISTRY. 

composition in the living system, which, in many cases, quickly 
terminates in death. Another case in point is the communication 
of the virus of smallpox, which, when introduced into the blood, 
reproduces its peculiar putrefaction throughout the system. 

1049. Products.— The chief products of putrefaction are hy- 
drogen, nitrogen, carbonic acid, ammonia, carburetted, sulphu- 
retted, and phosphuretted hydrogens, and acetic, nitric, and 
butyric acids. Other compounds also arise with the varying con- 
ditions. The gaseous combinations of sulphur and phosphorus 
are the chief causes of the offensive odor of putrefying bodies. 
In addition to these well-determined products, putrefaction gives 
rise to another class less tangible, but more baneful. The foul 
accumulations of neglected towns, and the decomposing organic 
matter of many swampy districts, give off invisible emanations 
known as miasms and malaria, which fill the air, and when in- 
haled, often occasion fatal fevers and epidemics. Of their compo- 
sition, nature, or mode of action, nearly nothing is known. 

1050. Prevention of Putrefaction. — As the presence of moist- 
ure, a favoring temperature, and access of air are essential con- 
ditions of putrefaction, if any of them are withdrawn, the effect 
is prevented. It is well known that the most perishable organic 
substances, both vegetable and animal, may be indefinitely pre- 
served by drying. Cold checks decomposition, and it is entirely 
arrested by freezing. So, if the prime inciter of change, oxygen, 
is excluded, putrefaction cannot take place. This fact is illus- 
trated by the general practice of preserving all kinds of alimentary 
substances, meat, fruits and vegetables, in vessels which exclude 
the air. It is not enough, however, to remove the oxygen from 
the surface of the body ; that which is diffused within it must be 
expelled, which is done by boiling, or in some cases by a lower 
heat. 

1051. Antiseptics are preventers of change — substances which 
act in various ways upon changeable bodies to preserve them. 
Common salt and saltpetre act by partial desiccation. They ab- 
stract water from the flesh, and hence concentrate the solution of 

of the action of putrescent bodies ? Examples. 1049. Mention the chief products 
of putrefaction. To what is the odor of putrefying bodies due ? What are other 
products of putrefaction? 1050. How is putrefaction prevented? How are or- 
ganic bodies preserved ? Examples. What is necessary to preservation ? 1051. 
What are antiseptics? Explain the action of salt and saltpetre. Of alcohol and 



PUTREFACTION AND DISINFECTION. 375 

albumen within ; by surrounding the meat with salt water, and 
partially expelling the air, putrefaction is counteracted. Alcohol 
and sugar act in a similar way, removing a large portion of water 
from flesh and fruits, and surrounding them with unchangeable 
liquids and sirups? which prevent the access of oxygen. 

: 1052. Other antiseptics act directly upon the albumen, coagu- 
lating and fixing it in unchangeable compounds. The sap and 
juices of all plants contain more or less of dissolved albumen, 
which, by its putrefaction, becomes an active cause of the decay 
of wood. Eapid drying or l seasoning ' renders the albumen 
inert, and the same object may be secured in less time by inject- 
ing the pores of the wood with any compound which coagulates 
the albumen. "Wood is rendered indestructible by a process ap- 
plied by Dr. Kyan, which consists in steeping it in a solution 
OT^coiTOsive sublimate (kyanizing). Boucherie cut into the trunks 
of living trees and introduced salts of iron, which were drawn up 
by the sap, and, impregnating the wood, increased its durability. 
Dried animal bodies are preserved from change by injecting in 
their veins corrosive sublimate, acetate of lead, chloride of zinc, 
and many other substances. These, like arsenic, are poisons. . As 
life consists in change, and these arrest change, they destroy life, 
and thus conserve the structures in which it was manifested. 

1053. Disinfectants.— A distinction is drawn between anti- 
septics and disinfectants — the former prevent putrefaction, the lat- 
ter arrest it; though some substances often act in both ways. 
Compounds rich in oxygen, and which, when mixed with putrefy- 
ing matter are decomposed, act as powerful disinfectants. The 
permanganates perform this office, rapidly destroying the odor of 
putrid matter, and oxidizing sulphuretted and phosphuretted hy- 
drogen. Nitric acid and several of the nitrates act powerfully in 
the same way. Fumes of nitrous acid and chlorine are efficient 
disinfectants. Chlorine is conveniently used in the form of chlo- 
ride of lime or soda ; the addition of a little sulphuric acid sets the 
gas free rapidly. In disinfecting rooms by fumigation with gases, 
it is to be remembered that they corrode all metallic surfaces. 
Vinegar, and especially wood vinegar, which contains a little creo- 
sote, is a valuable disinfectant. So also is sulphurous acid (fumes 

sugar. 1052. Of other antiseptics. Of seasoning. What is kyanizing ? Give 
Boucherie's experiment. How are animal bodies preserved, and why? 1053. 
What is a distinction between antiseptics and disinfectants ? Explain the action 



376 ORGANIC CHEMISTRY. 

of burning sulphur) ; it destroys sulphuretted hydrogen by oxidiz- 
ing it, and it also acts by absorbing oxygen. The disinfecting 
power of charcoal has been elsewhere noticed. 

1054. Natural Disinfectants. — We have seen that oxygen and 
ozone of the atmosphere and the carbonaceous element of the earth 
are natural disinfectants on a vast scale. Water, although favor- 
ing decomposition, is an invaluable agent for removing and finally 
destroying putrescent matters, and heat, although up to 140° a 
promoter of putrefaction, above that point, by becoming a dryer 
and disorganizer, destroys the sources and products of infection. 

§111. Fermentation. 

1055. When the ternary compounds, as sugar or starch, are 
exposed to the air, in a moist state, they exhibit but little tendency 
to change, and give rise to none of the effects of putrefaction. 
But if to a solution of sugar there be added a little putrefying flesh, 
blood, cheese, milk, flour paste, white of egg, or any albuminous 
substance in a state of decomposition, their action is communicated 
to the sugar, which is broken up into new compounds. When the 
putrefiable substances are considered with reference to the effects 
they produce upon the other class of bodies, they are called fer- 
ments, and the communication of that condition of change is known 
as fermentation. 

1056. Mode of Action of Ferment. — When changing nitro- 
genous matter acts upon sugar to decompose it, there is no combi- 
nation between the elements of the two substances. All that is 
communicated, therefore, is an impulse of motion. The collision 
of oxygen shatters the nitrogenous group ; its motion is communi- 
cated to the atoms which compose the sugar, thus overturning 
their nicely balanced affinities. But the sugar cannot, like albumi- 
nous compounds, take the infection and go on decomposing itself. 
It only acts as it is acted upon, and when the motion of the impel- 
ling body is exhausted, the action ceases. Two parts by weight 
of ferment only decompose a hundred parts of sugar. 

1057. Vinous Fermentation. — When the sweet juice of fruits 
or plants is exposed to the air at the temperature of 70° or 80°, in 

of the latter ? Give examples. 1054. What are great natural disinfectants ? What 
of water and heat? 1055. How is fermentation produced? What are ferments? 
1056. State their mode of action. When does it cease ? What proportion of fer- 




FEEMENTATION. 377 

the course of a few hours a change commences ; small bubbles rise 
to the surface, the liquid becomes turbid, and begins to ferment, 
or, as is commonly said, to 'work. 1 After a time the bubbles 
cease to rise and the liquid is no longer sweet, but has acquired a 
spiritous taste. If now it be distilled, an inflammable body is sep- 
arated, which is known as spirits of wine, or alcohol, a product of 
the decomposition of sugar. 

1058. Yeast — During the process of fermentation, a grayish, 
frothy, bitter liquid is produced, known ^ OQO 

. jig. 283. 

as yeast, When fresh, it is m constant 
motion, from the escaping gas, but 
when dried it loses 70 per cent, of its 
weight, and is converted into a honey- 
looking solid. Yeast is a minute spe- 
cies of plant. Under the microscope it 
is seen to consist of numberless small 
rounded cells. Each little globule con- . 

. Yeast Plant, showing how it 

Sists of an enveloping skin, or mem- Grows by Budding and by 
, n Tt • i • • internal Granules. 

brane of albuminous matter containing 

a liquid. The yeast cells grow or expand from the minutest mi- 
croscopic points (granules), and also bud off from each other, as 
shown in Fig. 283. They are never formed except from the de- 
composition of albuminous substances, and their fermenting power 
is supposed to be due to the nitrogen they contain. Whatever 
destroys the vitality of yeast, deprives it of the power of exciting 
fermentation ; hence when it is exposed to a temperature of 212°, 
its action is destroyed, and it is also checked by a cold of 10°. 
When yeast is dried and pulverized, or mixed with acids, alcohols, 
or alkalies, it also loses its power. 

1059. In what manner the yeast plant acts in fermentation is 
not known. The most probable view is that of Pasteue, who 
maintains that the essential condition of fermentation is the con- 
version of albuminous matter into the membranes of the globules, 
and the assimilation and decomposition of the sugar in the process 
of their gfowth. 

1060. Production of Alcohol. — When fruit sugar is acted upon 
by yeast, it is decomposed and gives rise to alcohol and carbonic 

raent is necessary ? 1057. Describe the vinous fermentation. 1058. TVhat are the 
conditions of yeast ? Of what does it consist ? 1059. State Pasteur's theory of 
yeast. 1060. What are the changes when sugars are acted on by yeast ? 1061. 



378 



ORGANIC CHEMISTRY. 



Fig. 284. 




Decomposition of Sugar. 



acid. Two atoms of alcohol and four of 
gSk/Zs /~\&& carbonic acid are produced, the breaking 

¥P<J (^ i@y vfi/w np into groups being shown by the accom- 
panying figures. 

1061. Diastase.— Malt.-— But the sugar 
itself may be a product of fermentation. 
When seeds are exposed to air and moist- 
ure at a suitable temperature, germination 
commences. This consists in a series of 
changes, of which the first is an alteration 
of a portion of the nitrogenous matter and 
the production of an ill-understood compound called diastase. 
This is an active ferment, and taking effect upon the starch 
changes it to sugar and dextrine. When barley is treated in this 
way it swells and becomes sweet. Diastase is formed and the 
barley is termed malt. When the germ is about half an inch long 
the process is arrested by heat, but the dextrine is not destroyed. 
One part of malt does not contain more than 3 i of diastase, but 
according to Peesoz and Paten 1 part of diastase is sufficient to 
change 2000 of starch. Hence one part of malt can convert the 
starch of four or five parts of barley into sugar and dextrine. 

1062. Brewing Beer.— In this process the crushed or ground 
malt is digested in water at 100° (malted), to extract all the solu- 
ble matter it contains. The liquid, which is termed sweet wort, is 
then boiled to coagulate the excess of vegetable albumen. Hops 
are added to impart aroma and a bitter flavor ; the cooled wort is 
then run into a fermenting vat, and yeast is added. In a few 
hours bubbles of gas begin to rise and the liquid becomes covered 
with a foam of yeast, which gradually hardens into a crust. This 
is called surface yeast — another portion falls to the bottom and is 
known as sediment yeast. The former requires a higher tempera- 
ture, and is apt to give rise to lactic acid and other acidulous prod- 
ucts. The globules of surface yeast are propagated chiefly by 
budding. Sediment yeast acts more slowly and at a lower tem- 
perature, generates no acid products, and propagates b/ granules. 

1063. Though a portion of the yeast is spent in fermentation, 

What is the first change in germination ? "What is the effect of diastase ? Describe 
malt. What is the effect of heat? Give the proportion of diastase. 1062. De- 
scribe the process of brewing beer. How does surface differ from sediment yeast ? 
1063. How is the process continued ? Name the constituents of beer. 1064. What 



FERMENTATION. 379 

a much larger quantity is formed from the nitrogenous matter of 
the grain in solution. The fermentation is continued several days, 
but is checked before all the sugar is converted into alcohol, as it 
would soon turn sour if the decomposition were complete. The 
liquid is now drawn off into casks, where it undergoes a second 
protracted fermentation (ripening), after which it is kept tightly 
closed from the air. It contains, in addition to the alcohol, a por- 
tion of saccharine, nitrogenous, and aromatic substances, together 
with various oils and mineral salts. 

1064. Lager Beer is freed from all nitrogenized products by a 
slow and long-continued fermentation ; hence it may be preserved 
for years without further decomposition. Before consumption it 
lies stored in vaults for months, from which circumstance its name 
is derived (lager, to lay). The difference in color of malt liquors 
is owing to the various degrees of heat employed in malting. Ale 
is made from pale malt, while that used for porter is partially 
charred, giving it a brownish color and bitter flavor. 

1065. Wines are obtained from the expressed juice of the 
grape and other fruits. The fresh grape juice, or must, is placed 
in vats in cellars, where the temperature is so low that the fer- 
mentation proceeds very slowly. Sometimes the wines are bot- 
tled before the fermentation is quite complete, and they continue 
to generate carbonic acid, which remains compressed within the 
liquid. If the carbonic acid is so abundant as to produce efferves- 
cence when uncorked, the wine is said to be ' sparkling ; ' if other- 
wise, it is termed ' still ' wine. The sweetness of wines is due to 
undecomposed grape sugar, the ferment being exhausted before all 
the sugar is changed. This excess of sugar preserves the wine 
from further decomposition, so that some of the sweet wines, such 
as Tokay and Muscadine, have been kept uninjured for a couple of 
centuries. When the sugar is wholly decomposed the wines are 
called ' dry? as Claret, Burgundy, Port, Sherry, &c. The acidity 
of wines is chiefly due to tartaric acid. Their flavor and aromatic 
qualities are owing to a volatile substance called oznantliic ether, 
which is developed during fermentation, and also to various other 
fragrant principles contained in the juice of the grape. Wines 
contain, in addition to the ingredients named, a proportion of 

is lager beer ? "What causes the difference of color in malt liquors ? Examples. 
1065. How are wines made? How do sparkling wines differ from still wines? 
What is the effect of undecomposed sugar? To what is the acidity of wines 



380 



ORGANIC CHEMISTRY. 




Plan of a Still. 



various albuminous, oily, and coloring matters, and a small 
amount of acetic and other vegetable acids. 

FlG-2 83. 1066. Distilled liquors are 

obtained by subjecting various 
fermented mixtures to distilla- 
tion. The plan of a still is repre- 
sented in Fig. 283 ; a is a furnace, 
o a retort, containing the liquid 
to be separated ; and d the con- 
denser of cold water surrounding 
the worm, through which the 
condensed liquid passes. When 
the fermented mixture is heated 
above the boiling point of alco- 
hol, 173°, that liquid rises with a 
portion of the water, passes over, and is condensed. It is then called 
spirits of wine, and when redistilled, rectified spirits of wine. The 
strongest commercial alcohol still contains some 10 per cent, of 
water, which can only be separated by adding chloride of calcium, 
or some other substance which has a powerful affinity for water. 
"When the water is entirely removed the alcohol is said to be ab- 
solute or anhydrous. 

1067. Brandy is derived from the distillation of wine ; rum from 
that of fermented molasses, and arraclc from the distillation of fer- 
mented milk. Whiskey is obtained from corn, rye, and potatoes, 
by first converting their starch into sugar, then into spirit, and 
distilling the product. Gin is produced from the distillation of the 
spirit of a mixture of barley and rye, and owes its peculiar flavor 
to juniper berries. 

1068. Viscous Fermentation. — When certain saccharine juices, 
such as those of beets, carrots, or onions, are exposed to the air at 
a temperature from 86° to 104°, fermentation takes place, and the 
sugar disappears, but instead of carbonic acid and alcohol, lactic 
acid, mannite, and a mucilaginous, gummy substance are formed, 
which render the liquid viscid and ropy ; it is hence called the 
viscous or lactic acid fermentation. Mannite is a substance of a 
weak saccharine taste, and is not changed to alcohol by fermenta- 

owing? Their flavor, &c ? Mention other ingredients of wines ? 1066 Describe 
Fig. 283. What is spirits of wine ? Rectified spirits of wine ? Absolute alcohol ? 
1067. What is brandy ? Rum? Arrack? Whiskey? Gin? 1068. Describe the viscous 



ALCOHOL AKD ITS DERIVATIVES. 381 

tion. It is the chief ingredient of manna, a kind of sugar which 
exudes from a species of ash tree in Southern Europe, and is used 
as a medicine. 

1C69. Lactic AcidjC^HjO^HO, so called because it occurs in 
sour milk, is a colorless, sirupy, very acid liquid, which combines 
with bases, forming a class of salts, the lactates. 

§ IY. Alcohol and its Derivatives. 

ALCOHOL. 

1070. Spirits of Wine— Ethylic Alcohol, C 4 H 6 2 , sp. gr. of 

liquid at 32° 0.815: of vapor 1.613.— Alcohol is a colorless, mobile 
fluid, having a pleasant, fruity smell, and a burning taste. It is 
very volatile, about one fifth lighter than water, and has a strong 
attraction for that liquid, which causes it to absorb moisture from 
the air, thus rendering it valuable as an antiseptic. It is highly 
combustible, producing intense heat without smoke, and is there- 
fore well adapted to burn in lamps for chemical use. 

1071. Alcohol has great value as a solvent, as it acts upon 
many substances which water does not dissolve, and is easily 
separated from them on account of its extreme volatility. It boils 
at 173°, and has never been frozen, although at — 166° it becomes 
viscid. In a concentrated form it is a potent poison, but when 
sufficiently diluted, it acts upon the animal system as a stimulant. 
Taken freely in this form it produces inebriation, and is the active 
principle of all intoxicating liquors. Alcohol, till of late, has been 
regarded as procurable only by organic decomposition — the de- 
struction of sugar — but it is now made artificially by the synthesis 
of its elements. 

1072. Derivation of Acetic Acid. — If the vinous fermentation 
is not checked at the proper time, it passes on to a second stage, 
the acetous fermentation ; the liquid loses its spirit and quality, 
and becomes sour. Oxygen is absorbed, and the alcohol converted 
into vinegar or acetic acid, C 4 H 3 3 ,HO. Pure diluted alcohol 
does not absorb oxygen when exposed to the atmosphere ; it is 
affected only by adding some matter in a state of change, or which 

fermentation. "What are mannite and manna sugar ? 1069. What is lactic acid? 
1070. Give the composition of alcohol. Its properties. 1071. State some other 
properties of alcohol. 1072. What is the acetous fermentation ? Give the com- 



382 



ORGANIC CHEMISTRY. 



Fig. 284. 



absorbs oxygen. The action proceeds slowly at first, bnt by de- 
grees a peculiar body, a kind of slimy vegetable mould, is formed, 
which is known as mother of vinegar, and which acts something 
like a ferment to hasten the process. 

1073. Aldehyd. — The change from alcohol to acetic acid is 
not direct — an intermediate substance is formed, called aldehyd 
4 H 4 2 , so named from aZ-cohol ^M^-drogenated, or deprived of 
hydrogen. This substance may be produced by the gradual oxidation 
of alcohol, in various ways, or by transmitting a mixture of alcohol 
and air through a porcelain tube at a low red heat. Aldehyd is a 
highly volatile, inflammable liquid, with a pungent, apple-like odor. 

1074. When a few drops of alcohol are placed 
in a cup, its vapor will mingle with the air. If 
now a red hot coil of platinum wire be intro- 
duced into the cup, Fig. 284, the oxidation of the 
vapor commences (471), pungent odors of aldehyd 
are given off, and the wire is kept at a red heat 
by the continued oxidation. If the coil be sus- 
pended over the wick of an alcohol or ether lamp, 
Fig. 285, it will continue to glow for hours after 
the flame is extinguished, from the same cause. 

1075. The Quick Vinegar Process. — As oxy- 
gen is the active agent in acetification, the rapid- 
ity of the process will obviously depend upon the 
abundance of its supply. If the air comes in con- 
tact with but a small portion of the liquid, months 
may be required to produce the change. In the 
quick vinegar process the liquid is made to trickle 
over beech shavings, which have been previously 
soaked in vinegar, and placed in a tall vessel. In 
Fig. 286 A A represents such a tub, near the top 
of which is a perforated shelf d d, through which 
the liquid falls. The shavings, loosely packed at 

&, rest upon a perforated shelf just above c c c, which are apertures 
for admission of air; the glass tubes in the cover allowing its 
escape. By this arrangement a vast surface is exposed, the absorp- 
tion is very rapid, and the acetification is completed by a few 




Oxidation of 
Alcohol. 



Fig. 285. 




Flameless Lamp. 



position of vinegar. How is the mother of vinegar formed ? 1073. What is alde- 
hyd, and why bo named ? Its properties ? 1074. What is the effect of a hot plati- 
num coil upon alcohol vapor ? 1075. Upon what does the rapidity of acetification 



ALCOHOL AND ITS DERIVATIVES. 



383 



Fig. 286. 




The Quick Vinegar Process. 



repetitions of the process. Any fermented liquid, as a mixture of 
crude spirits and water, may be used. 

1076. Properties of Acetic Acid. — Pure acetic acid is a color- 
less, intensely sour liquid, 
.which has a pungent odor, 
and blisters the skin. Mixed 
with various proportions of 
water it forms vinegar of (lif- 
erent degrees of strength; 
common table vinegar con- 
tains from three to four per 
cent, of acetic acid. Acetates 
are salts of acetic acid, all 
very soluble. Verdigris is an 
acetate of oxide of copper, 
which forms a green paint. 
Acetate of lead (sugar of lead) 
is soluble in pure water, and 
has a sweet, astringent taste. 
Acetates of alumina, iron, 
and ammonia, are used in dyeing and in medicine. 

1077. Ether 3 C 4 H 5 (Sulphuric Ether).— When equal weights 
of oil of vitriol and alcohol are heated in a retort, a vapor passes 
over which maybe condensed into a limpid fluid, called ether from 
its volatility, and sulphuric ether, because in obtaining it sulphuric 
acid is employed. In composition ether is alcohol less the ele- 
ments of an atom of water, which is separated by the sulphuric 
acid. 

1078. Ether is colorless, with a fragrant odor, and a hot, pun- 
gent taste. It is so volatile that it disappears when poured through 
the air from one vessel to another, and when placed upon the 
hand, produces cold by rapid evaporation. It boils at 96°, or when 
exposed to the air* in summer, and is very combustible, burning 
with more light than alcohol and some smoke. Its vapor, when 
mixed with air, is explosive. It readily dissolves fats and oils. 

1079. Alcohols and Ethers.— By the chemist the substances 

depend ? Describe the quick vinegar process, Fig. 286. 1076. State the properties 
of acetic acid. "What are acetates ? Examples. 1077. "What is the composition of 
ether ? How is it produced ? From what is the term sulphuric ether derived ? 
1078. What are the properties of ether ? 1079. why are the alcohols and ethers in- 



384 ORGANIC CHEMISTRY. 

we have just been considering have an interest as types of large 
and important classes of compounds, having analogous properties 
and relations. The term alcohol was formerly restricted to the 
vinous product just described, but it has now become generic and 
embraces a large group of homologous substances (915). All 
organic compounds of carbon, oxygen, and hydrogen which unite 
with acids and separate the elements of water, forming ethers, are 
known as alcohols. There is a class of ethers derived from the 
alcohols by distilling them with different acids, as nitric ether, 
butyric ether, carbonic ether, &c. 

1080. The composition of Formic Acid is C 2 H, 3 , HO or hy- 
drated teroxide of formyle. It is a clear, pungent, strongly acid 
liquid, which was first obtained by distilling the bodies of red ants 
{formica rubra) in water, hence its name formic acid. It is this 
acid which causes the painful, stinging sensation, produced by 
handling the nettle, as its leaves are covered with little, sharp, 
hollow spines, with elastic cells at the base filled with the liquid. 

1081. Chloroform, 2 HC1 3 , is a terchloride of formyle, and is 
prepared by distilling alcohol with a solution of chloride of lime. 
It is a colorless, volatile liquid, of a strong, agreeable odor, and a 
sweet, penetrating taste. It dissolves sparingly in water, but free- 
ly in alcohol and ether. It is extensively employed in medicine, 
but for this purpose it should be perfectly pure, as the fatal effects 
which have sometimes attended its use are doubtless chiefly owing 
to its contaminations. It should be colorless and free from a chlo- 
rous smell, or any unpleasant odor, when a few drops are evapor- 
ated on the hand. 

1082. Anaesthetics. — Chloroform and ether are the most im- 
portant representatives of a class of bodies, the vapor of which 
when inhaled produces temporary insensibility to pain, or anes- 
thesia ; these substances being known as ancesthetics. For a hun- 
dred years physicians have sought for agents that would so deaden 
consciousness, that surgical operations might be performed with- 
out inflicting pain ; chemical science has at length furnished the 
inestimable boon. 

1083. Amylic Alcohol.— In the crude spirit obtained by distil- 

teresting to the chemist ? What does the term alcohols include ? 1080. How is 
formic acid obtained, and what are its properties ? 1081. What is chloroform, and 
how prepared? Its properties? What precautions should he observed? 1082. 
What is said of anaesthetics ? 1083. Describe fusel oil. How is it regarded, and 



ANIMAL STRUCTURES. 385 

ling grain and potatoes, there is generated a disagreeable, pungent, 
oily body, known as fusel oil. It is regarded as the hydrated ox- 
ide of the radicle amyle CxoHnOgHO. It has a persistent odor, 
a burning taste, and, though existing in but small proportion in 
distilled liquors, it increases their intoxicating effect. 

1084. Artificial Fragrant Ethers.— By the action of the yari- 
ous acids upon the alcohols, a great number of fragrant ethers are 
produced. TThen amy lie alcohol is distilled with oil of yitriol and 
acetate of potash and mixed with six times its bulk of alcohol, it 
giyes the product known as c pear oilf which has the odor and 
flayor of the Jargonelle pear. If bichromate of potash is used in 
place of the acetate, apple oil is produced, and in the same manner 
other acids produce the flayor of melons, quinces, bananas, oranges, 
&c, which are much used by confectioners as 'flayoring essences. ' 
The flayoring principles of yarious flowers, and of spirituous liquors, 
are also produced in this way, and extensiyely employed in perfume- 
ry and in the manufacture of wines and other liquors from alcohol. 

1085. Mercaptans — Sulphur Alcohols. — The ogygen of the al- 
cohols may be replaced by sulphur, forming sulphur alcohols, 
which haye a strong affinity for mercury, and are hence called 
mercaptans. They haye a yery offensiye odor, resembling gar- 
lic. The radical Xakodyl, C 4 H 6 As, is a colorless, yiscous liquid, 
emitting fumes which, from their strong affinity for oxygen, take 
fire spontaneously when exposed to the air. It is highly poisonous 
and produces an intolerable stench. It is of much chemical in- 
terest, as it was the first organic base which played the part of a 
simple metallic body and could replace hydrogen. 



CHAPTER XXIII. 

A X I il A L PRODUCTS. 

§ I. Animal Structures. 

1086. Composition of Flesh. — The muscular parts of animals 
consist of fibrin, separated into bundles by membranes, and into 

what are its properties? 1CS4. How are artificial fragrant ethers produced? 
How is pear oil obtained ? Apple oil, &c. ? What other flavoring principles are 
thus produced ? 1085. "What are mercaptans ? TVhat of kakodyl? 10S6. Of what 

17 



Water. 


Albumen and Fibrin. 


Gelatin. 


Total solid matter. 


74 


20 


6 


26 


. 75 


19 


6 


25 


71 


22 


7 


29 


. 76 


l; 


5 


24 


73 


20 


7 


27 


. 79 


14 


7 


21 



386 ORGANIC CHEMISTRY. 

larger separate masses by cellular tissues in which fat is deposited. 
The fleshy mass is penetrated by a network of blood vessels called 
veins, and the whole is distended by water, which forms about three 
fourths of the weight of the meat. The composition of the mus- 
cular flesh of different animals, according to Bea^de, is as follows : 

Beef, 
Veal, . 
Mutton, . 
Pork, . 
Chicken, . 
Cod, . 

1087. Juice of Flesh. — The true color of flesh fibrin is white, 
but it is ordinarily stained reddish by the coloring matter of the 
blood. Yet the liquid of meat is not blood; when that has been 
withdrawn from the animal, there remains diffused through the 
muscular mass a peculiar liquid known as the juice of flesh. It 
consists of the water of flesh, containing about 5 per cent, of dis- 
solved substances, one half of which is albumen and the remainder 
a mixture of several compounds not yet examined. The juice of 
flesh may be separated by finely mincing the meat, soaking it in 
water and pressing it. The solid residue is white, tasteless, and in- 
odorous. The separated juice is uniformly and strongly acid, from 
the presence of lactic and phosphoric acids ; hence it is in an oppo- 
site state to that of the blood, which is invariably alkaline. 

1088. Creatin. — The juice of flesh contains the savory prin- 
ciples which give flavor to meat, and which cause it to differ in 
different animals. It also contains two nitrogenous crystallizable 
compounds, called creatin and creatinin. Creatin (0 8 H 9 N 8 O 4 +2 
Aq.) is a neutral substance, while creatinin (CgH-jN^Os) is a pow- 
erful organic base of a similar nature with theine and caffeine. 
Inosic acid is a sirupy liquid derived from meat, and has an 
agreeable taste of the juice of flesh. Inosin or muscle sugar is 
found in the juice of flesh, the heart yielding it most readily. It 
has a sweet taste, is soluble in water, and forms crystals. 

1089. Gelatin. — When the tendons, ligaments, cartilages, skin, 

does the muscular part of animals consist ? What of the #eshy mass ? 1087. What 
gives color to flesh fibrin ? Is the juice of meat blood ? What is the juice of flesh f 
How may it be separated, and what is the residue ? Mention the difference be- 
tween the juice of flesh and blood ? 1088. What does the juice of flesh contain. 
What of creatin and creatinin ? Describe inosic acid. Inosin. 1089. How is gel- 



ANIMAL STRUCTURES. 387 

and bones of animals are for some time boiled in water, a sub- 
stance is extracted which, on being cooled, hardens to a jelly. 
This is called gelatin. It is a nitrogenized compound, with the 
formula O 13 H 10 jSr 2 O 5 S ; but, unlike the albuminous substances, 
it is never found in plants, nor is it a constituent of the blood. 
Some chemists maintain that it is formed by the process employed 
to obtain it, and has no real existence in the animal organism. 
Pure gelatin is colorless, transparent, inodorous and insipid. In 
cold water it gradually softens and swells, but does not dissolve 
till heated. It is insoluble in alcohol, ether, and the fixed and 
volatile oils. 

1090. Isinglass is the purest form of commercial gelatin, 
and is obtained chiefly from the air bladders of fish, as the stur- 
geon and cod. It is extensively employed as an article of diet in 
the form of jelly. The gelatin from cartilage is termed chondrin, 
and differs somewhat from ordinary gelatin. 

1091. Dietetical Value of Gelatin. — Gelatin, in the form of 
calves-foot jelly, blanc-mange, &c., is much used as an article of 
food, and it is also the chief thickening element of soups produced 
by long boiling of animal substances. Though a nitrogenous body, 
it is not of the protein type. It is regarded as a product of the 
partial decomposition of albuminous bodies in the system, but as 
incapable of replacing them when taken as aliment. The French 
attempted to feed the inmates of their hospitals on gelatinous ex- 
tract of bones. Murmurs arose, and a commission, with Magenme 
at its head, was appointed to investigate the matter. They re- 
ported gelatin as, dietetically, almost worthless ; but it is proba- 
bly of some value, especially to invalids, as a diluent of nutritious 
food. 

1092. Glue is a form of gelatin extracted from bones, and the 
refuse skin, hoofs, and ears of cattle, by boiling them in water, 
and evaporating the solution. Good glue is hard, brittle, translu- 
cent, of a brownish color, and absorbs three or four times its 
weight of water without dissolving. Size is an undried or gelat- 
inous glue, made from the parings of parchment — the thinner 
kinds of skins. When applied to paper, it fills up its pores, and 
thus prevents the spreading of ink. 

atin obtained ? What is further said of it ? State its properties. 1090. What of 
isinglass ? Chondrin ? 1091. What is said of the dietetical value of gelatin ? 
What of the French investigation ? 1092. What is glue ? Its properties ? What 



388 ORGANIC CHEMISTRY. 

1093. Leather. — Gelatin combines with tannic acid, forming 
the basis of leather. The skins, first softened by soaking, are 
placed in vats containing lime water, which dissolves the sheaths 
of the hairs, and permits their ready removal. "When freed from 
hair, and soaked in a weak solution of acid, to neutralize the lime, 
they are transferred to tan pits. These contain a weak solution 
of bark, the tannic acid of which slowly penetrates the skin, and, 
uniting with the gelatin, forms the leathery compound. The 
operation is slow, requiring many months, as no quickening pro- 
cess yet contrived produces so excellent an article. Currying 
consists in impregnating the skin with oil, and working it into a 
pliable state. 

1094. Bones. — Bones consist of gelatinous tissue, into which 
mineral matter has been deposited until it possesses a stony hard- 
ness. The mineral substances are chiefly phosphate and carbonate 
of lime. The phosphate predominates in the higher animals ; in 
the lower, the carbonate. The amount of mineral substances in 
bones increases with age ; in the adult man, it forms about two 
thirds of the weight of the bone. 

1095. If a bone is soaked in diluted chlorohydric acid, the 
mineral salts are dissolved out ; the organic matter remaining as 
tough, flexible, nearly transparent gelatin, having the same form 
as the bone. But if we submit a bone to strong heat, the animal 
portion is burned out, and the earthy part remains. The bone is 
then brittle and falls to pieces at the slightest touch. Hence, bony 
structures owe their tenacity to the organic element, and their 
hardness and stiffness to the mineral substances of which they 
consist. The bones of fish contain a large proportion of organic 
matter, which accounts for their flexibility. 

1096. The Teeth are similar in composition to the bones, but 
contain less organic matter. The enamel of the teeth contains, in 
addition to phosphate and carbonate of lime, a proportion of fluoride 
of calcium. 

1097. Horny matter, which forms the hair, wool, feathers, 
claws, nails, and hoofs of animals, has about the same ultimate 

is size, and for what used? 1093. How is leather prepared? What is currying? 
1094. Of what do bones consist ? What of their mineral constituents ? 1095. "What 
results if a bone be steeped in dilute chlorohydric acid ? If exposed to strong 
heat? To what do they owe their different properties? What of the bones of 
fish ? 1096 Of the teeth ? 1097. What of horny matter ? To what is the color of 






ANIMAL SECRETIONS. 389 

composition as gelatin, but resembles more closely the albumin- 
ous bodies in its reactions. It contains but a small proportion of 
saline matter, is insoluble in water, and is dissolved with difficulty 
by caustic alkalies. The substances composed of it owe their pecu- 
liar colors to the animal oils which they contain. The skin is 
closely allied to horny matter in its composition. 

1098. Shells. — The shells of the mollusca, oysters, clams, &c, 
and of the eggs of birds are composed almost wholly of carbonate 
of lime ; while those of the Crustacea, as lobsters, crabs, &c, gen- 
erally consist of only half their weight of carbonate of lime, the 
remainder being animal matter with a small proportion of phos- 
phate. 

§ II. Animal Secretions. 

1099. Animal Secretions are the liquids separated from the 
blood and poured out by various organs of the living body for 
special purposes ; as tears to moisten the eyes, gastric juice for 
solution of food, &c. 

1100. Milk.— This familiar liquid is secreted from the blood 
of the females of the class mammalia for the nourishment of their 
young. It is the only substance prepared by nature as an article 
of food, which furnishes all the materials for the development of 
the various organs and compounds of the young animal. Its com- 
position is, therefore, a matter of much physiological interest. An 
analysis of fresh cow's milk gave 

Water, 88.30 

Casein, ...... 4.82 

Milk Sugar, ..... 8.39 

Butter, ...... 3.00 

Salts, ...... 0.49 



Solid Matter, 100.00 

11.70 

The five great types of food are thus represented, viz. : 1st, the 
aqueous; 2d, the albuminous; 3d, the saccharine; 4th, the olea- 
ginous ; 5th, the saline. 

1101. The Oily Element. — In respect to its sugar, casein, and 
salts, milk is a solution, but with reference to its oily part it is an 

hair, feathers, &c., due? 1098. Give the composition of shells. 1099. What are 
animal secretions ? 1100. What is said of milk as food ? What are its constitu- 
ents? What does it represent? 1101. How does milk appear as seen by the mi- 




390 OKGANIC CHEMISTRY. 

emulsion. The butter of milk is diffused 
through it in the form of exceedingly mi- 
nute globules, which when viewed by the 
microscope appear floating in a trans- 
parent liquid, Eig. 287. The milk glo- 
bules are lighter than water, and hence, 
when the milk is allowed to stand undis- 
turbed, they slowly rise to the surface, 
forming cream. Each little globule is 
invested by a thin membrane of casein, 
which is ruptured by the agitation of 
churning, causing the butter to cohere in a separated mass. 

1102. Spontaneous Curdling. — When milk is allowed to stand 
for a short time it sours and curdles ; that is, its casein changes 
from the dissolved to the solid state. This is brought about by a 
series of interesting changes, originating in the unceasing activity 
of atmospheric oxygen. Casein is insoluble in water. But in the 
milk it exists combined with soda, and this compound dissolves in 
water. Now when fresh milk is exposed to the air its oxygen 
seizes upon a portion of the casein and changes it to a ferment ; 
this takes effect upon the milk sugar and converts it into lactic 
acid, which causes the sourness of the milk. "When a sufficient 
quantity of the lactic acid is thus formed, it seizes upon the soda, 
takes it away from the casein, and forms lactate of soda. The 
casein, thus set free, shrinks in bulk and gathers into an insoluble, 
curdy mass. 

1103. Artificial Curdling. — In making cheese the milk is 
curdled artificially, and in different countries various substances 
are employed for this purpose. Almost any acid will curdle milk, 
and vinegar, lemon juice, dilute muriatic acid, &c, are used to 
produce this effect. But the substance most generally employed 
for this purpose is rennet — the lining membrane of the stomach of 
a calf, salted and dried. The rennet is soaked in water, or whey, 
which, being added to milk at a temperature of 95°, coagulates it 
promptly. It was formerly supposed that the action of the gastric 
juice of the rennet produced the change, but the membrane acts 
with equal promptitude when washed thoroughly free from all 

croscope? How is cream formed? Butter? 1102. What is the cause of the 
curdling of milk! Explain the chemical changes. 1103. State the effect of acids 
upon milk. What is generally used to curdle milk ? To what is the change 



ANIMAL SECRETIONS. 391 

acid. The change is due to the decomposing animal matter of the 
rennet. This converts milk sugar to lactic acid, which neutralizes 
the soda, and precipitates the casein. Only a minute quantity of 
rennet is necessary ; according to Berzelitjs, one part of the 
membrane being sufficient to coagulate thirty thousand parts of 
< milk. 

1104. Cheese. — By the act of curdling, the milk is divided 
into two parts : first, the curd, comprising all the casein, a large 
portion of oil, and a trace of sugar of milk, with some water ; and 
second, the ichey, or fluid part, containing the bulk of water, the 
sugar of milk, and a small, variable proportion of oily matter. Of 
the saline matter in milk, the phosphates of lime and magnesia 
exist in the curd, while the remaining salts are found in the whey. 
The curd, separated from the whey and prepared in various ways, 
forms, when pressed, cheese. 

1105. Renal Secretion {Urine). — This liquid is separated from 
the arterial blood by the kidneys, and contains the chief soluble 
waste products of the body. In fasting it is feebly acid, but 
during digestion it becomes slightly alkaline. When left undis- 
turbed for a time (which varies with the temperature), it putrefies, 
acquires a powerful alkaline reaction, and gives off ammonia. 
This excretion is the outlet of the nitrogenous products of the de- 
composed tissues, and of the saline constituents of the body. 

1106. Urea, C 2 H 4 N 2 2 , is the chief product of the kidney 
excretion. It is a neutral body, crystallizes in slender prisms, and 
forms compounds with salts. It is not formed in the kidneys, 
but is separated by them from the blood. Uric, or Uthic acid, 
C 10 H 4 N" 4 O 6 , is a small constituent of human urine, but abounds 
in the excretion of birds and serpents. Urate of ammonia is the 
chief constituent of guano. It is this acid, principally, in combi- 
nation with soda, which accumulates around the joints in gout, 
and it is also a constituent of several of the stony concretions 
known as urinary calculi. Hippuric acid is another nitrogenous 
body found in urine. 

1107. The openings from the surface of the body are lined 
with what are known as mucous membranes, which are constantly 

owing? What proportion of rennet is necessary? 1104. Into what does curdling 
divide the milk? Give the constituents of the curd. Of the whey. What is cheese? 
1105. What is the origin of urine ? State its different conditions. Of what is it the 
outlet ? 1106. What of urea ? Where is uric acid found ? What is said of it in con- 



392 ORGANIC CHEMISTRY, 

moistened by a viscid secretion called mucus. This is insoluble in 
water, and yields a glairy product called mucin. 



CHAPTER XXIV. 

CHEMISTRY OF FOOD. 

§ I. Chemistry of Bread Making. 

1108. Objects of Culinary Art.— Organized substances de- 
signed as human food — grains, roots, fruit and flesh — are many of 
them not adapted for this purpose in their natural condition, and 
to become digestible, require to be mechanically and chemically 
changed. This is effected chiefly by water and heat. These 
agencies soften some substances, dissolve others, and enable us to 
prepare palatable and nutritious dishes from the crude, tasteless, 
or noxious bodies furnished us by Nature. 

1109. Preparing the Dough for Bread.— This is usually done 
by first mixing suitable proportions of flour, water, yeast, and salt 
into a stiff batter, and exposing it for an hour or two to a gentle 
heat. The water hydrates the starch, dissolves the sugar and albu- 
men, and moistens the dry particles of the gluten, causing them to 
cement together all the ingredients into a cohering mass. The 
yeast now causes an active fermentation, converting the sugar of 
the flour into alcohol and carbonic acid. It also converts a por- 
tion of the starch into sugar. The carbonic acid is diffused 
throughout the mass in the form of minute bubbles, which, being 
caught by the tenacious gluten, cause the dough to swell and 
rise. "When the fermentation is sufficient, the dough is kneaded 
into loaves for the oven. Leavened bread is made by substituting 
for yeast a ferment of sour flour paste (leaven). 

1110. Changes of Bread in Baking. — When the prepared 
dough is exposed in an oven to a temperature of 350°, it loses 
from 10 to 16 per cent, of its weight by evaporation. But the 

nection with gout and urinary calculi? 1107. What of mucus? 1108. What changes 
must many organized bodies undergo to fit them for food ? How are they effected ? 
1109. How is bread dough prepared ? What changes does the yeast produce 1 
Why does the bread rise ? What is leavened bread ? 1110. How does heat affect 



CHEMISTRY OF BREAD MAKING. 393 

loaf increases in bulk to about twice its size. This is due to the 
expansion of the carbonic acid contained in its pores, the conver- 
sion of water into steam, and the vaporizing of alcohol, which is 
driven off in the gaseous form. Attempts have been made in 
large bakeries to condense and save the alcohol, and a weak spirit' 
was obtained, but it seems not to have repaid the trouble of 
its collection. The surface of the loaf is first dried and then dis- 
organized. The roasting converts the starch into gum, and pro- 
duces a peculiar, brown, soluble substance, known as assamar. 
If the heat is excessive, a thick carbonaceous crust is formed, 
which prevents the penetration of heat, and produces a raw 
interior. 

1111. As the temperature within the loaf cannot rise above 
212°, no changes go on there except such as are produced by the 
heat of the watery vapor. This is sufficient to stop the fermenta- 
tion, destroy the bitter principle of the yeast, and kill the yeast 

. plant. In baking, about y 1 ^ of the starch is converted into gum, 
the rest remaining chemically unchanged. The gluten, though 
not decomposed, loses its tough qualities, and unites closely with 
the starch paste. 

1112. New and Stale Bread — In newly baked bread the crust 
is dry and crisp, while the crumb is soft and moist, but after a 
short time this condition of things is quite reversed ; the brown 
products of the roasting process attract moisture, and the crust grows 
daily softer, while the crumb becomes hard and dry. This appar- 
ent dryness, however, is not caused by loss of water, but by com- 
binations going on among the watery and solid atoms of the bread. 
That the moisture has only passed into a state of concealment may 
be shown by exposing a stale loaf in a closely covered tin vessel 
for half an hour to a heat of 130°, when it will again have the 
appearance of new bread. Well-baked wheaten bread contains on 
an average about 45 per cent, of water, so that the bread we eat is 
nearly one half water. 

1113. Aerated Bread. — A new method has lately come into use 
in which carbonic acid is forced,under high pressure,into the water 

the bread ? To what is its increase in bulk owing ? "What attempts are mentioned ? 
Describe the changes of the crust. 1111. To what are the changes within the loaf 
due ? In what do they consist ? 1112. "What differences are mentioned between the 
crust and crumb ? To what is the dryness of the latter owing ? How is it proved ? 
What proportion of water does bread contain ? 1113. How is aerated bread made ? 

17* 



394 ORGANIC CHEMISTRY. 

employed for making the dough. The intermixture of the mate- 
rials, or kneading, is effected by machinery under great pressure. 
As soon as the pressure is removed, the dough, rises from the ex- 
pansion of the compressed carbonic acid. 

1114. Use of Chemical Substances. — Fermentation is often 
replaced by a quicker method of raising the dough, through the 
agency of chemicals. Bicarbonate of soda and chlorohydric acid 
are used, the soda being thoroughly incorporated with the flour, 
and the acid added to the water used fqr mixing. The acid com- 
bines with the alkali, forming common salt, and carbonic acid is 
set free, which distends the dough. To ensure neutralization, the 
ingredients should be pure, the proportions correct, and the mix- 
ture perfect. Soda powders consist of tartaric acid and bicar- 
bonate of soda. The soda combines with the acid, producing tar- 
trate of soda, and liberating carbonic acid. Cream of tartar is ex- 
tensively employed. "When sour milk is used, the carbonic acid is 
set free by lactic acid. 

1115. Phosphated Bread. — The high price and pernicious 
adulteration of cream of tartar have created a demand for a sub- 
stitute. Prof. Hoesford claims to have found it in phosphoric 
acid, or acid phosphate of lime, which combines with the soda, 
setting free carbonic acid, and producing phosphate of soda and 
lime ; both normal constituents of the body. This preparation is 
now furnished as a yeast powder. 

1116. Salts of Ammonia are sometimes employed for raising 
dough, but the gases formed are apt to communicate a disagree- 
able hartshorn flavor to the bread. All these chemical methods 
have one serious disadvantage — the gas is set free too suddenly 
to produce the best effect. The cautious use of chemicals, when 
pure, in bread making may be tolerated on grounds of convenience, 
but their employment by careless housekeepers in the commercial 
form is highly injudicious, as they are apt to be contaminated with 
injurious, and even poisonous impurities. 

1117. Deterioration of Flour. — Flour tends to deteriorate by 
time. It is very hygroscopic, and the absorbed water gradually 

1114. By what is fermentation often replaced? What chemicals are mentioned ? 
Explain their action ? What precautions are necessary ? What of soda powders ? 
Sour milk? 1115. What is Prof. Hoesford's substitute for cream of tartar? 
Describe its action. 1116. What of salts of ammonia ? State the disadvantage of 
all these chemicals. What is said of the use of chemicals ? 1117. Why does flour 



CULINARY CHANGES OP ALIMENTARY SUBSTANCES. 395 



Fig. 28a 



impairs the tenacity and fineness of the gluten. Oddlixg has 
shown that it is converted into a substance resembling diastase, 
which changes the starch of the flour into dextrine and sugar. 
Such flour of course makes a heavy, sodden bread ; flour, there- 
fore, should be preserved in a state of the utmost dryness. Liebig 
has ascertained that flour thus damaged may be greatly improved 
by lime water ; 100 parts of flour are mixed with 26 or 27 of lime 
water, and sufficient water added to form dough. The lime re- 
moves all acidity from the dough, somewhat augments the pro- 
portion of water absorbed, and restores the original qualities of the 
gluten. Common salt and alum cause dough to absorb more 
water than it would otherwise do. 

§ II. Culinary Changes of Alimentary Substances. 

1118. Effects of Boiling.— In boiling the food is surrounded 
by a powerful solvent, which more or less completely extracts cer- 
tain constituents of the food. Vegetable acids, 
sugar, gum, and vegetable albumen are all 
soluble in water, and by boiling are partially 
removed. The tougher parts are made ten- 
der, the hard parts softened, and the connec- 
tions of the fibres and tissues loosened, so as 
to be more readily masticated, more easily 
penetrated by the saliva and juices of the 
stomach, and therefore more promptly and 
perfectly digested. 

1119. Breaking up of the Starch Grains.— The structure of 
starch grains has been described. They consist of layers or coats 
arranged concentrically around a 
point called the Jiilum. If one of 
these grains be strongly compressed 
between two plates of glass it 
breaks apart into several pieces, as 
seen in Fig. 288 ; but under the 
joint action of heat and water the 
membranes are torn asunder, or ex- 
foliated, by internal swelling, as 
represented by Fig. 289. 




Starch Grain Fractured. 




Starch Grams Ruptured by Boiling. 



deteriorate? "What has Oddling shown? How should flour be kept ? What is 
Liebig's remedy? "What change doe3 the lime effect ? 1113 How does boiling 
change food? 1119. Wliat is the structure of starch grains? "What do figures 



396 



OKGANIC CHEMISTRY. 



Fig. 290. 



1120. Changes of Starch.— When starch is diluted with twelve 
or fifteen times its weight of water, and slowly heated, all the 
grains burst on approaching the boiling point, and swell to such a 
degree as to occupy nearly the whole volume of the liquid, form- 
ing a gelatinous paste. If a little of this be diffused through cold 
water, and examined with the microscope, it will be seen that the 
starch grains have greatly changed. They have increased to 
twenty or thirty times their original size ; the concentric lines are 
obliterated ; the membrane of the grain is ruptured, and its in- 
terior matter has escaped. "When starch is boiled in water for a 
considerable time it gradually changes, first into gum and then 
into sugar. A cold starch jelly left to stand, either closed or ex- 
posed to the air, undergoes the same change, but to effect it, 
months are required. 

1121. How Potatoes are Changed by Cooking. — The potato 
is composed of three fourths water, and one fourth solid matter, 

which consists chiefly of starch. "When 
examined by the microscope the tissue is 
found to consist of a mass of cells, each 
inclosing some 10 or 12 starch grains, 
loosely situated, as shown in Fig. 290, 
and surrounded by the potato juice, 
which contains albumen. If potatoes be 
of good quality they boil dry, or mealy, 
as it is termed; but their juice does not 
separate or boil out. It is absorbed by 
the starch grains, which form a com- 
pound with it and swell up, so as completely to fill and even burst 
the cells, as seen in Fig. 291. When the juice of the potatoes is 
only partially absorbed by the starch they are watery or waxy. 
Potatoes when boiled in water do not form a jelly, like common 
starch, because the starch grains are protected, partly by the coats 
of the cells in which they are inclosed, and partly by the coagu- 
lated albumen. 

1122. Quality of Water for Culinary Purposes.— Soft water, 




Potato Cells Before Boiling. 



illustrate ? 1120. How is a solution of starch affected by heat ? What changes aro 
seen with the microscope ? When starch is boiled for some time, what changes 
occur? What is the effect of exposing starch jelly to the air? 1121. Of what is 
the potato composed ? What does Fig. 290 illustrate ? What becomes of thejuice 
when potatoes boil mealy ? When are they watery I Why do not potatoes form 



CULINARY CHANGES OF ALIMENTARY SUBSTANCES. 397 



Fig. 291. 




After Boiling. 



or that which is free from dissolved mineral matter, makes its 
way into organized tissues with much more readiness than hard 
water. Its higher solvent power better fits it 
also to act as a vehicle for conveying food into 
the living system. In culinary operations, 
where the object is to soften the texture of 
animal and vegetable matter, or to extract 
from it and present in a liquid form some of 
its valuable parts, as in making soups, broths, 
or infusions (as of tea and coffee), soft water 
is the best. But there are cases in which the 
solvent action of soft water is too great, as 
sometimes upon green vegetables, which it 
makes over tender, destroying the firmness 
that is essential to the preservation of their juices, which 
are dissolved and extracted, rendering the substance propor- 
tionately tasteless. In those cases therefore, where we do not 
desire to dissolve out the contents of a structure, but to preserve 
it firm and entire, hard water is better than soft. To prevent this 
over-dissolving action, soft water is often hardened by the addition 
of common salt, which also hinders the evaporation of the flavor- 
ing principles. 

1123. Constituents of Flesh. — When lean meat is chopped fine 
and soaked in cold water, there remains a solid residue consisting 
of the fibres, tissues, &c. It is white, tasteless, and inodorous. 
All the savory constituents of the flesh were contained in its juice, 
and were entirely removed by cold water. If the watery infusion 
thus produced be boiled, a clear, yellowish liquid is obtained which 
has the aromatic taste and other properties of soup made by boil- 
ing the flesh. When evaporated and dried, a soft, brown mass, 
amounting to 12 or 15 per cent, of the weight of the original dry 
flesh, is left, having an intense flavor of roast meat. This extract, 
when dissolved in hot water, gives to it all the properties of soup > 
retaining the peculiar taste of the flesh from which it was derived. 

1124. Action of Heat upon the Constituents of Flesh. — The 



a jelly ? 1122. "What is said of soft water as a solvent ? When should it be used ? 
"When is its solvent power too great ? When is hard water to be preferred in cook- 
ing? What effect has the addition of salt? 1123. What is the result when lean 
meat is chopped fine and soaked in cold water? State the effect of boiling this 
liquid infusion ? What of this product when dried and evaporated ? 1124. Describe 



398 ORGANIC CHEMISTRY. 

effect of boiling upon fibrin is to render it bard and tougb. Heat, 
as we have seen, changes liquid albumen to the solid condition, 
and renders it insoluble in water, either hot or cold. Fat is, of 
course, liquefied by the action of heat and, at a high temperature, 
is resolved into various acid and acrid bodies. 

1125. The Cooking of Meat. — The first effect of applying a 
strong heat to fresh meat is to contract its fibres, press out a por- 
tion of the juice, and prevent the escape of more by partially 
closing the pores. In preparing meat for food, it is desirable that 
it should retain the ingredients of its j nice ; and this will depend 
much upon the method of culinary procedure. If the meat be in- 
troduced into the water when briskly boiling, the albumen at its 
surface, and to a certain depth inward, is immediately coagulated ; 
thus enclosing the mass in a crust which prevents the juice from 
escaping, and also from being weakened and dissolved by the ex- 
ternal water penetrating within. The albumen coagulated within 
the meat also forms a protective sheath around the fibres, and 
thus prevents them from becoming shrivelled, tough, and hard by 
boiling. If, on the contrary, the meat be placed in cold water, 
and the temperature slowly raised to boiling, a portion of the 
savory and nutritive juices is dissolved out, and the meat becomes 
proportionally poorer for the loss, while, at the same time, the 
fibres grow hard and tough. Whether the meat be surrounded 
by hot water, or exposed to heat in any other way, as soon as the 
water-proof coating is formed, the further changes are effected by 
internal vapor, or steam. In roasting or talcing, therefore, the 
fire should at first be quite hot, as meat, when exposed to a slow 
heat, becomes dry and unsavory, from the constant escape of its 
juices through the open pores. 

1126. Soups. — In the preparation of these, our object is the 
reverse of that just considered. We desire to take tbe nutritive 
and savory principles out of the meat, and obtain them in a liquid, 
or soluble form. To obtain the best liquid extract of meat in the 
form of soup, broth, or tea, the flesh is finely chopped and placed 



the action of heat upon the constituents of flesh. 1125. Mention its first effect. 
"What is desirable >n cooking meat ? How does boiling water act upon meat ? 
"What is the result of placing meat in cold water and slowly raising its tem- 
perature? After the water-proof coating is formed, how are the further changes 
produced? "Why, in roasting or baking meat, should the fire be at first quite hot ? 
1126. What is the object in preparing soups ? How is this best effected ? "Why is 



CHEAIISTKY OF SOILS. 399 

in cold water, which i3 then slowly heated and kept boiling for a 
few minutes, when it is strained and pressed. The meat should 
not be boiled long, as the effect is to coagulate and render insolu- 
ble the ingredients extracted by the cold water, and which should 
have remained dissolved in the soup. 

1127, The Effect of Salt, when rubbed upon raw fresh meat, 
is to contract its fibres, thereby pressing out the juices, so that a 
brine is soon formed without the addition of any other liquid. 
This brine contains a large proportion of the albuminous con- 
stituents and mineral salts of the meat, the removal of which 
impoverishes it and renders it incapable of complete or healthful 
nutrition. Salted meat is, therefore, dietetically much inferior to 
fresh meat. 



IAPTEE XXV. 

CHEMISTRY OF SOILS. 

1128. A few years since a remarkable impulse was given to 
the subject of Agricultural Chemistry, chiefly through the labors 
of Prof. Liebig. The first effect of the movement was to create 
extravagant expectations in regard to what chemistry could ac- 
complish for agriculture. It was supposed that the farmer had 
only to obtain an analysis of his soil, and by comparing the re- 
sults with tables of the composition of crops, he could, by supply- 
ing the missing constituents, place his agriculture at once upon a 
simple, scientific, and successful basis. Experience quickly dissi- 
pated this fallacy, and then came a reaction, in which agricultural 
chemistry was denounced as misleading and worthless. The truth 
in this case lies between the extremes. "While chemistry cannot 
be made a sole guide in agriculture, it can contribute important 
assistance, and is indispensable to the enlightened and most suc- 
cessful practice of the art. 

1129. Prof. Axdebsox states that it is only in rare instances 
possible to connect together the chemical composition and prop- 
erties of the soil; that analysis is frequently incapable of dis- 

long "boiling injurious ? 1127. How does salt affect raw meat ? Why are salted 
meats less nutritious than fresh? 1123. what is said of Liebig? What was the 
first effect of this impulse ? Its reaction ? Where does the truth lie ? 1129. Give 



400 ORGANIC CHEMISTRY. 

tinguishing between a fertile and a barren soil ; that it discloses 
only a part of the conditions of fertility, and that with each ad- 
vancement in the accuracy of its processes the difficulties have in- 
creased, rather than diminished. Still, in the study of soils we 
cannot dispense with the aid that chemistry affords. 

1130. Origin of Soils. — The mineral elements which compose 
the chief mass of soils are derived from the disintegration of rocks 
by air and moisture, heat and frost. Of course the composition 
of the rock determines that of the soil derived from it — an argilla- 
ceous rock producing a soil abounding in clay ; a calcareous rock 
in lime ; a silicious rock in sand. There is hence a relation be- 
tween soils and the rocks from which they are derived, but it is 
made so obscure by the transportation and admixture of materi- 
als, as to be discoverable only by the well-instructed geologist. 

1131. In the crumbling down of rocks into soil, the decom- 
position is not complete. Besides a portion of liberated alkalies 
and alkaline earths, the sands and clays contain large amounts of 
potash, soda lime, and magnesia, locked up in combination, so as 
to be imperfectly or not at all available to growing vegetation. 
-Yet the same forces, which disintegrated the rocks are still at 
work upon these constituents of soils, carrying forward the same 
decomposing changes, and gradually liberating the needed ele- 
ments of fertility. 

1132. Variety of Soils — Soils are named from their predom- 
inating element, as sandy, argillaceous, calcareous. Those con- 
taining excess of sand are light and porous; water escapes 
through them ; manures are wasted, and in drought plants lan- 
guish and die. On the other hand, an excess of clay makes- a soil 
stiff, heavy, and retentive. A due admixture forms the loamy soil 
in which the evils of both extremes are corrected. It is suffi- 
ciently open to permit the free extension of the roots, and the ad- 
mission of air, while moisture and manures are retained. 

1133. Physical Properties of Soils. — The most important of 
these are specific gravity, tenacity, power of retaining moisture, of 
absorbing and retaining heat, and of absorbing moisture, carbonic 
acid, ammonia, and oxgyen from the air. These properties are 
most powerfully influenced by drainage, deep and subsoil plough- 
Prof. Anderson's testimony. 1130 How do soils originate? What is said of 
their composition ? 1131. What do the sands and clays contain ? How are they 
fertilized? 1132. Describe the varieties of soil. 1133. Mention their physical 



CHEMISTRY OF SOILS. 401 

ing, mixture of soils, &c. But it is impossible to alter the physical 
character of soils without at the same time affecting their chemical 
properties. 

1134. Chemical Properties. — These relate to the composition, 
state of combination, and solubility of soil ingredients. The ele- 
ments, which most abound in soils, are not the most important. 
They contain the food of plants in but small proportions. If the 
soil is deficient in any of the constituents of plant food, or if they 
are locked up in inaccessible forms, plants will not grow, and the 
soil is said to be barren. If long cropping has removed any of the 
available constituents, it is brought to the same state, but is then 
said to be exhausted. 

1135. Two Sources of Plant Food. — Plants live a double life. 
As will be explained in the following chapter, they have a twofold 
nutrition ; deriving mineral food from the soil, and organic from 
the air. How much comes from each source is an important 
question in practical agriculture, and has given rise to a lively con- 
troversy among agriculturists. The atmospheric elements, car- 
bonic acid, and ammonia may come also from the decomposi- 
tion of organic matter in the earth, and the question at once 
arises, in fertilizing a soil, "Which class of constituents is most 
necessary ? 

1136. Variation of the Mineral Elements While the or- 
ganic constituents of plants are generally uniform, upon an exam- 
ination of their ashes it is found that different classes are marked 
by the prevalence of certain mineral elements. Some abound in 
potash, others in lime ; some in phosphates, and others in silica. 
Different parts of the same plant have also their predominating 
elements. We have here one reason why all crops are not 
suited to the same soil, and why one crop may succeed where an- 
other fails. 

1137. Liebeg's Mineral Theory — Starting from these facts, 
Liebig maintains that the fertilization of soils is chiefly a question 
of the addition of such mineral substances, in a form suitable for 
absorption, as plants specially require. He holds that the organic 
ingredients are abundantly furnished by the air, but that the 

properties. How are they influenced? 1134. What of their chemical properties ? 
When are soils barren? and when exhausted? 1135. Explain the twofold life of 
plants. What question is in controversy ? 1136. State the variations in the min- 
eral eiements. For what does this account? 1137. What is Liebig's mineral 



402 ORGANIC CHEMISTRY. 

mineral constituents are not supplied in sufficient quantity, and in 
available condition to the roots. Other chemists, represented by 
Lawes and Gilbeet, of England, maintain the opposite view. They 
hold that the store of mineral substances in the soil is generally 
abundant for the wants of crops ; but that the atmospheric supply 
is not, and requires to be supplemented by ammoniacal manures, 
or those yielding nitrogen to the plant. 

1138. The truth seems to be, that while plants if allowed suffi- 
cient time can extract organic materials from the air, and attain a 
vigorous growth, yet if it be desired to rapidly increase their de- 
velopment, manures yielding ammonia and carbonic acid to their 
roots must be furnished. This policy, however, if long continued 
will exhaust the soluble inorganic constituents of the soil ; hence 
in all permanent systems of agriculture, mineral fertilizers can no 
more be neglected than organic. 

1139. Lime as a Fertilizer. — Fertilizers are divided into min- 
eral and organic. Lime is one of the most important of the first 
class. It is used in the forms of marl and chalk, but most com- 
monly as slaked lime. It* acts in various ways, but its least im- 
portant use is as plant food, for there are probably few soils which 
have not sufficient lime for this purpose. It acts mechanically to 
loosen tenacious soils, and chemically to decompose the silicates, 
liberating the alkalies, which are locked up in combination. It 
decomposes vegetable matters, converting their nitrogen into am- 
monia. It changes inert substances, so as gradually to render 
them useful to vegetation ; decomposes noxious compounds ; neu- 
tralizes baneful acids ; sweetens vegetation, and improves the qual- 
ity of nearly all crops. 

1140. The compounds it forms in soils are generally insoluble ; 
its action is therefore slow, often requiring two or three years to 
produce its full effect. At first it may diminish crops, and does 
so invariably when applied in over doses. On light soils, deficient 
in vegetable matter, it should be used sparingly. 

1141. Gypsum is a valuable fertilizer for some crops, but the 
manner of its action is not known. Salts of potash, soda, and 
ammonia are excellent when they can be afforded. Experience 
verifies what theory affirms — that ashes are most valuable. They 

theory? How is it controverted ? 1138. "What is said of organic and mineral fer- 
tilizers? 1139. Into what are fertilizers divided? Describe the uses of lime. 
What of it as plant food? 1140. Explain its action upon soils. 1141. What of 



CHEMISTRY OF SOILS. 403 

restore to the soil the mineral matters which the crops remove, 
while the alkali they contain has the same beneficial effect as lime, 
with the superior advantage of acting immediately. Crushed 
bones form an exceedingly valuable manure, as their animal mat- 
ter yields nitrogen, and the mineral matter phosphate of lime. 
When bones are treated with sulphuric acid, a soluble phosphate 
is produced, which acts with more promptness than the neutral 
phosphate. 

1142. Farm Yard Manure. — With the exception of the small 
portion retained in the body, it is evident that the excretions 
of an animal represent the complete composition of its food, and 
if all restored again to the soil, would afford the restitution neces- 
sary to prevent exhaustion and maintain fertility. The solid ma- 
nure of animals consists of the indigestible and insoluble portions 
of their food. Liquid manure, on the contrary, represents the 
assimilated portion — that which was incorporated into the system, 
but was afterward decomposed and escaped from it in a soluble form. 
Liquid manure has, therefore, a far higher value as a fertilizer. 

1143. Guano consists of the accumulated excretions of sea 
birds, deposited on rainless islands, and is sometimes found in masses 
a hundred feet deep. Its chief constituents are ammonia and phos- 
phate of lime, which amount in the best kinds to from J to i its 
weight. They occur in a soluble form, and its effect upon crops is 
therefore immediate and powerful. 

1144. The golden rule of agriculture is to restore to the soil, 
in the shape of manure, exactly what it has lost in the crop. By 
failing to heed this principle millions of acres of the choicest land 
in this country have been utterly exhausted, and millions more are 
undergoing the same ruinous process. The skilful farmer econ- 
omizes every source of fertility. His manure heaps are sprinkled 
with gypsum, dilute sulphuric acid, or some other absorbent, to 
prevent the escape of ammonia ; liquid excretions are preserved in 
tanks, and no particle of it wasted; compost heaps gather and 
utilize all forms of refuse, and while the accumulation of filth and 
noisome odors is prevented, the soil is enriched and culture made 
remunerative. Fertilizers are the farmer's motive power; with 
them he can do everything, without them nothing. 

gypsum salts of potash, &c. Ashes ? Bones ? 1142. Why is animal manure so 
valuable? Give the comparison between solid and liquid manures. 1143. What 
of guano? 1144. What is the golden rule of agriculture 2 How does the skillful 



PAET IV. 
PHYSIOLOGICAL CHEMISTRY. 



CHAPTER XXVI. 

VEGETABLE CHEMISTRY. 

§1. Chemical and Vital Forces. 

1145. Having noticed the properties of the chief organic com- 
pounds, we now pass to the chemistry of living beings, and the 
chemical relations of the organized kingdoms to each other and to 
the inorganic world. 

1146. The Mystery of Life. — However viewed, the^ranscen- 
dent miracle of nature is Life. "Whether considered as supporting 
the spiritual fabric of mind above, or as rooted in the organic 
world below, it is alike wonderful. Springing from ethereal airs and 
yet invincible ; constantly perishing, and yet abounding in earth, 
air, and sea; forever conquered by death, yet evermore tri- 
umphant — c strongest and weakest of the things God has made,' it 
is not surprising that it has been regarded as unlike all else in na- 
ture. It was but natural that the living system should be looked 
upon as the seat of a potent agency — the mysterious Vital Princi- 
ple — which built up, maintained, and used the organic form, and 
subdued all surrounding forces. 

1147. The Vital Force. — There has been a reluctance to con- 
sider the science of organized beings from a chemical point of view, 
as it was said the vital force here comes into play which overrides 

farmer manage ? 1145. What are we now to consider ? 1147. Why has there heen 
a reluctance to consider organized beings from a chemical point of vieAV ? Why is 



GEE^^ATION AND CELL GROWTH. 405 

chemical laws and is itself inscrutable. But this idea is no longer 
admissible. In one sense all forces are mysterious ; yet they act 
with regularity, and whatever obeys law can be investigated, 
Though we cannot penetrate to the essential nature of any force, 
yet we may learn the manner of action and mutual connections 
of all forces. Vital force overcomes affinity, and so mechanical 
force overcomes gravity, but neither chemical force nor gravity 
is suspended. There are no unresisted forces in nature ; indeed, 
it is only by their constant resistance and overcoming that forces 
are called into exercise. 

1148. Vital force is not denied, but in the present state of sci- 
ence it does not mean an independent principle, or force, like heat, 
or magnetism ; c it is a collective term embracing all those causes 
upon which the vital phenomena depend ' (Liebig). There are 
doubtless great obstacles in studying the changes of the living sys- 
tem, but as Prof. Miller remarks : . ' The difficulty depends not so 
much upon the obscurity which enshrouds the nature of life — for 
the essential nature of all forces is equally inscrutable, but rather 
upon the extreme delicacy of the arrangements by which such 
changes are effected, and which are liable to injury from a multi- 
plicity of causes that have hitherto eluded scrutiny.' 

1149. Having banished the superstition which blindly ascribed 
all things to an inscrutable vital force, and thus stopped inquiry 
at the outset, science has demonstrated that living beings are not 
aliens and exceptions in the universe, but parts of its wonderful 
plan ; that they are governed by its laws, and are to be studied by 
the same methods, and with the same success, as the other 
phenomena of nature. 

§ II. Germination and Cell Growth. 

1150. The Vegetable Embryo. — Every plant springs from a 
seed, and every perfect seed contains the rudiment of a new plant, 
called the germ or embryo. In some varieties it is so complete 
that the microscope reveals its structure— root, stem, and leaves. 
The minute plant lies imbedded within the seed, surrounded by 
a protecting mass, which consists chiefly of starch and gluten. 

this idea inadmissible ? How do forces operate ? 114S. What is understood by vital 
force ? From what arises the difficulty of studying the changes of the living sys- 
tem ? 1149. What has science demonstrated ? 1150. Describe the embryo. What 




406 PHYSIOLOGICAL CHEMISTRY. 

Fig. 292, shows the germ in Indian corn and its proportion to 
the surrounding matter of the seed, which 
forms the principal bulk of ordinary cultivated 
grains. "Wrapped in this envelope, the embryo 
remains at the disposal of external agents. In 
certain conditions it continues at rest and tor- 
pid; but when these conditions are changed, 
it suddenly awakens from its slumber, puts 

Germ of Indian Corn . „ . , , , . , , , . 

forth a new power and begins to grow ; this is 
called germination. 

1151. Chemistry of Germination.— The embryo during growth 
derives its nourishment from the surrounding body of the seed. 
To convey this nourishment requires a moving medium. This 
office is performed by water ; hence the first condition of germi- 
nation is exposure of the seed to moisture, the absorption of which 
causes it to swell and increase in bulk. But the nourishment can- 
not be transferred except in a soluble form, and the starch and 
gluten are insoluble in water. To remove this difficulty nature 
resorts to a beautiful process which necessitates the second con- 
dition of germination — the access of air. Oxygen is thus absorbed, 
and acting upon the gluten, changes a minute portion of it into 
diastase, which, taking effect upon the starch, transforms it first 
into dextrine, or gum, and then into sugar. A portion of sugar is 
oxidized into acetic and carbonic acids— the temperature rising — 
and the remainder is transferred to the embryo. This is now as- 
similated by the germ, but it has no power to organize the ele- 
ments which contribute to its nourishment. Heat also influences 
germination. Each kind of seed requires a certain temperature, 
although it varies in different species, from just above the freezing 
point, to 100° or 110°. Light impedes germination, the deoxi- 
dizing rays tending to fix the carbon and thus check the formation 
of carbonic acid. 

1152. Development cf the Embryo. — Fed by its store of nu- 
triment, the embryo expands ; one part, the radicle, shoots down- 
ward to form a root, while the other, the plumula, or stem, ex- 
tends upward to the surface, as shown in Fig. 293. But when the 
stem appears above the ground, and expands its earliest leaves, 

does Fig. 292 show ? When does germination take place ? 1151. What nourishes 
the embryo during growth? Describe the first process of germination. The seo- 
ond. Of what power is the germ destitute ? 1152. What are the radicle and plu- 



GERMINATION AND CELL GEOWTH. 



407 



the plant passes into another stage of existence, and a new order 
of phenomena is manifested. No longer depending for nour- 
Fig. 293. ishment npon ready made food furnished by the 
seed, it begins to exert a formative power — the 
true vegetable function — and produce from the min- 
eral elements of the earth and air such organized 
compounds as it may require. 

1153. Minute Mechanism of Growth. — Vegeta- 
ble growth takes place through the action of certain 
bodies termed cel]s, which are very minute, closed 
bags or sacs, usually ranging in size from ^ to TJ Vo 
of an inch in diameter. "When uncompressed, as in 
the pith of elder, Fig. 294, or the pulp of fruit, Fig. 
295, they have a rounded form ; but when closely 
crowded by others, they become flat-sided, angular, 
and elongated, Fig. 296. 

1154. Structure and Formation of Cells. — The 
cell consists of an outer membrane, or cell-wall, 
which incloses a lining sac, and within this is a dot 
or nucleus. In plants the outer membrane consists 

Emb°ryo! g of cellulose, and the inner one of nitrogenous matter. 



Pig. 294 



Fig. 295. 



Tig. 296. 





Cells of Elder Pith. 



Cells of Fruit Pulp. 



Ceils of a Rootlet. 



This contains a viscid, albuminous liquid called protoplasm, in 
which float numerous small grains. At the rupture, or death of 
the parent cell, these grains are set free, and each one becomes 
the germ or nucleus of a new cell. At its surface a delicate mem- 



mula ? How does the young plant now proceed ? 1153. Describe the mechanism 
of growth. 1154. Explain the structure of cells. Their formation. How do they 




408 PHYSIOLOGICAL CHEMISTRY. 

brane appears, which gradually extends much beyond the original 

germ, giving rise to the cell cavity. Cells also multiply by division. 

The contents of the cell (1) become separated (2), and then a par- 

Fig 297 tition is formed across it (3) producing two cells ; 

Qthe subdivision is thus carried on indefinitely. 
Cells also increase, as before noticed, by pro- 
cess of budding and branching (1058). All the 
various tissues and structures of vegetables are 
(^iT^^ b u ^t U P °f these cells, much as a wall is form- 
V>_y^y ed of bricks or stones ; with the difference that 
the living structure forms its own bricks. 

1155. The Cell Wall.— Though the cell 
membrane is without the slightest trace of pores 
or openings, yet, like all organic membranes, it 
is permeable to fluids. The cell wall exhibits 
the remarkable property of retaining its liquid 
contents, while it permits the free transudation of other fluids. 
The passage of the fluids takes place by osmose. The termina- 
tions of the rootlets of plants consist of active cells which absorb 
water from the soil, and this, ascending through the fine woody 
tubes, passes through many millions of partitions before reaching 
the leaves. 

1156. Cells are the little workshops of the organized world. 
By the free circulation of fluids, the raw materials are conveyed 
into them, and there transformed into organized matter. Different 
cells are specially adapted to produce different substances ; some 
forming starch, others oil, wax, acids, &c. 

§ III. The Chemistry of Vegetable Growth. 

1157. Architecture of the Tree. — In speaking of germination, 
we saw that the embryo is stamped with a 'polarity — a tendency 
to develop in opposite directions ; one part is to live in the earth, 
the other in the air. There is a deep significance in this architec- 
ture of the tree. Its stem, supported by widely-extended roots, 
rises high in the air ; it divides into branches, and subdividing 
into boughs and twigs, finally terminates in myriads of little, flat, 
green plates, called leaves, which are generally mounted upon 

multiply? 1155. How is the passage of fluids effected? 1156. What is the office 
of the cells ? 1157. How does the germ exhibit polarity ? What is said of the ar- 



THE CHEMISTRY OF VEGETABLE GROWTH. 409 

slender foot stalks. The idea evidently is to obtain the largest 
amount of surface which the material will afford consistent with 
the proper degree of strength. Furthermore, the atmosphere is 
ever in motion, so that by the swinging of the boughs, and the 
trembling of the leaves on their elastic foot stalks, the surface 
contact with the air is heightened to the utmost. 

1158. Not without its purpose is all this admirable contrivance, 
and one might well anticipate that the economy of vegetation is in 
some way closely linked with the properties of the atmosphere- 
A microscopic examination of the leaf confirms this idea, by 
showing that its surface is covered by thousands of little open- 
ings (stomata), which are fitted either for the exhalation or inha- 
lation of gases. 

1159. Food of the Plant.— "Water, containing dissolved a por- 
tion of the gases of the air — carbonic acid and ammonia — together 
with a minute proportion of earthy matter from the soil, is ab- 
sorbed by the mouths of the rootlets (spongioles), and enters the 
vegetable organism as crude sap. In this dissolved form the min- 
eral or inorganic world flows into the organic. The mineral 
solution, upon its entrance, mingles more or less with the or- 
ganized juices, so that unmixed, crude sap is never found in the 
plant. 

1160. Nourishment from the Air. — Eising through the capil- 
lary tubes of the vegetable structure, the crude sap passes upward 
to the leaves. It there exhales its excess of water into the air, 
becomes condensed and digested ; new products are formed, and 
the sap is said to be elaborated. But the plant derives also a 
portion of its nourishment directly from the air, in the form of 
carbonic acid gas. Though the proportion of this gas in the at- 
mosphere is small, yet the vast leaf surface — each leaf being cov- 
ered by a film of moisture which is highly absorbent of carbonic 
acid — enables the foliage to withdraw it in considerable quantity 
from moving masses of air. 

1161. The largest portion of the nutriment of the plant is, how- 
ever, procured immediately from the soil. Carbonic acid, carbon- 
ate of ammonia, and nitric acid, are dissolved out of the atmos- 
phere by the falling rain, and penetrating the earth, enter the plants 

chitecture of the tree ? How is the surface contact heightened ? 1158. Explain the 
design of this arrangement. - 1159. How does the plant receive its food ? 1160. 
"What becomes of the sap? How does the foliage absorb carbonic acid? 1161. 
18 



410 PHYSIOLOGICAL CHEMISTRY. 

by the roots. Should they be furnished to the roots by decompo- 
sition of organic matters in the soil, these again may be traced 
back to the air, so that although plants may be said to receive 
their food chiefly through the soil, they derive it from the air. 
The vegetable kingdom, and the atmosphere which surrounds it, 
consist of the same chemical elements. 

1162. Chemical Changes in the Leaf. — The green leaves 
digest the crude sap ; they consist of living cells, which carry on 
active chemical changes, translating matter from the inorganic to 
the organic state. It was shown by Peiestley, in 

the last century, that the foliage of plants in the 
sunshine gives off oxygen gas to the surrounding 
air. This may be seen by exposing a few fresh 
leaves to the sunshine in an inverted glass vessel, 
filled with water, Fig. 298 ; the air bubbles which 
arise and collect at top are oxygen. Carbonic acid 
thus enters the leaf, and oxygen is set free, the car- 
bon being retained. The leaves decompose the car- 
bonic acid, separating the carbon, which is fixed in 
newly-formed organic compounds. This is probably Leaves Exhai- 
the source of all the carbon in plants. 

1163. Water and ammonia are decomposed to furnish the hy- 
drogen and nitrogen of organic substances ; the requisite oxygen 
being supplied by both carbonic acid and water. From these ele- 
ments the leaf constructs gum, dextrine, starch, albumen, cel- 
lulin, and many other products which are contained in the elab- 
orated sap, and conveyed to different points of the vegetable 
organism. 

1164. Plants are thus universally instruments for separating 
oxygen — machines of deoxidation. It is through these operations, 
and by grouping the products thus formed, that the plant be- 
comes a constructor of organized bodies. 

1165. Formation of Acids. — How the changes take place we 
do not actually know, but it is not difficult to see in what way 
they are probably performed. The atom of carbonic acid may be 
taken as the starting point. It consists of three elementary atoms, 

"What is said of the nourishment of the plant immediately from the soil ? 1162. 
what was proved by Priestley? How may it be shown? Describe the chem- 
ical changes? 1163. Explain the further processes of the leaf. 1164. How does 
the plant construct organized bodies? 1165. How are acids supposed to be 




THE CHEMISTRY OF VEGETABLE GROWTH. 411 

one of carbon, and two of oxygen. ATopart of a vegetable or animal 
structure contains for one atom of carbon more than tico atoms of 
another element — most of them contain less. Organization there- 
fore begins by separating oxygen from carbonic acid. The vege- 
table acids are lowest in the organic scale, and arise from the 
first steps of deoxidation. For example, carbonic acid consists 

CO 

of C0 2 , or COO, and dry oxalic acid of C 2 3 , or ^qq. If, there- 
fore, from a group of two atoms of carbonic acid, but a single 
atom of oxygen be separated, the remainder represents oxalic acid. 

1166. The process may now be carried a step higher, resulting 
in the formation of a more complex acid. If from a group of 
two atoms of oxalic acid two more atoms of oxygen are removed, 
and the hydrogen from the two atoms of water added, we have 
malic acid C 4 H 2 4 . To produce an atom of oxalic acid, but a 
single atom of oxygen is set free ; for an atom of malic acid, six 
are liberated. 

1167. Production of Sugar, Starch, &c. — The products first 
formed are marked by an excess of oxygen, like carbonic acid, and 
have properties analogous to that acid. But as the process is car- 
ried farther, a higher and neutral class of bodies appears — the 
acids pass into sugar and its congeners. To produce an atom of 
sugar an atom of carbonic acid is taken, COO ; half its oxygen is 
separated, making CO ; an atom of water is then decomposed, and 
its hydrogen made to replace the separated oxygen atom, thus 
COEL Twelve atoms of carbonic acid, and twelve of water, 
changed in this manner, give C 12 H 12 12 , or the glucose group 
without its combined water. 

1168- It has been stated that this class of bodies, sugar, starch, 
cellulin, &c, are remarkable in having their oxygen and hydrogen 
in the exact proportion to form water, so that they may be regarded 
as hydrates of carbon. On this view we have but to suppose all 
the oxygen removed from the carbonic acid, and the resulting car- 
bon joined directly to water, to explain the synthesis of these sub- 
stances. It will be noticed that the deoxidizing process is carried 
much farther here than in the case of acids: to produce an 
atom of sugar, C 12 H 12 12 , 24 atoms of oxygen are set free. 

formed ? Example. 1166. How the more complex acids ? 1167. What is said of 
the products first formed ? What class now appears ? How are they produced ? 
1168. Give the synthesis of the bodies. 1169. Describe the formation of fats and 



412 PHYSIOLOGICAL CHEMISTRY. 

1169. Production of Fats and Oils. — As these bodies con- 
tain an excess of hydrogen and a minimum of oxygen, being 
thus the reverse of acids, it is obvious that the deoxidizing pro- 
cess has been here carried much further. For the production of 
an atom of stearine, C x Y 4 H X 10 O 32 , 144 atoms of carbonic acid and 
98 of water must lose their oxygen, which would liberate no less 
than 326 atoms of this gas. In forming the pure hydrocarbons, 
the reduction of hydrogen and carbon is complete, all their oxygen 
being set free. 

1170. Production of Nitrogenous Compounds. — The forma- 
tion of these is perhaps less simple. The large proportion of car- 
bon and hydrogen is of course obtained by deoxidation. But the 
complex albuminous group is probably built up by the coupling of 
simpler compounds (923). It is supposed that all the higher or 
more complex organic compounds are thus formed; and 'albu- 
men, casein, and the organic bases are regarded as coupled com- 
pounds, which they certainly are, although we do not yet know 
the copula belonging to them ' (Liebig). 

1171. Changes of the Starch Group.— Physiologically, dex- 
trine, sugar, starch, and cellulin are one thing. Several of their 
modifications are strictly isomeric, and they are all convertible into 
each other by the addition or subtraction of an atom or two of 
water. In a chemical point of view they might all be formed in 
the leaf with equal ease ; but their diversities of physical character 
require their production in a certain order. Dextrine, gum, and 
sugar are probably first formed in the elaborated sap. These are 
soluble, and therefore easily transported from point to point of 
the vegetable organism. Cellulin is the fixed, insoluble member 
of the group, and, therefore, cannot be produced at first ; it is 
only formed where it is required to furnish tissue. Starch is a 
kind of intermediate product ; being insoluble, and taking the 
shape of minute grains, it is fitted to be temporarily deposited as a 
kind of nutritive stock, to be redissolved and transferred to other 
places for use, wherever necessity requires. We saw an example 
of this in the case of germination. Starch is the form in which the 
food for the future embryo is stored up in the seed, to be trans- 
formed into dextrine and sugar, and then again into the cellulin of 
the young germ. 

oils? What is s aid of the pure hydrocarbons? 1170. How are the nitrogenous 
compounds formed? 1171. How are dextrine, sugar, starch, and cellulin regarded 
chemically? When are dextrine, gum, and sugar formed, and why? Cellulin? 



THE CHEMISTRY OF VEGETABLE GROWTH. 413 

1 1 72. Changes of the Albuminous Group. — In the living cell 
the nitrogenous protoplasm seems to be the active agent, or medium 
of vital changes. We saw its power of inducing transformation 
in the starch group, when treating of fermentation. It forms 
the lining of the cell, and the cellulin is deposited under its influ- 
ence to form the permanent wall or cell fabric. "When the cell is 
thus matured, its nitrogenous matter leaves it and is attracted on- 
ward into the newly growing parts. It is thus explained why so 
small a quantity of albuminous substance plays so all-important a 
part in the vegetable economy, and why such a mere trace of it is 
found in the woody structure of plants. The matured heart of 
trees yields but the faintest indication of nitrogen, while the sap- 
wood and young growing parts always contain a small proportion, 
which accounts for their tendency to rapid decay. These sub- 
stances are at length nearly all withdrawn from the fabric of the 
plant, and laid up in the fruit and seed. Being transferred to the 
animal system, their relations are changed, and they play the same 
part that the starch group did in the vegetable structure. 

1173. Plants in Apartments.— As plants are purifiers of the air 
in a double sense, withdrawing its noxious carbonic acid and re- 
turning its life-giving oxygen, it might seem that they would be 
very efficacious for this purpose in inhabited rooms. They per- 
form this office in the day time, and are also useful in exhaling 
moisture into the air, which, in houses warmed by hot air, is often 
a most important service. But at night the regular vegetable 
function is suspended; carbonic acid is no longer withdrawn; 
oxygen is no longer set free, and the effect of the plant upon the 
air is due to leakage through the leaves of the gaseous contents of 
the sap. Carbonic acid will therefore be given off in very small 
amount at night, and just to that degree, vegetation is injurious in 
sleeping rooms. It is erroneous to speak of plants as respiring — 
exhaling oxygen by day, and carbonic acid by night. 

What of starch ? 1172. Describe the office of the protoplasm. What is said of the 
nitrogenous matter? Why does the sapwood and young growing parts decay 
rapidly ? What further changes do the nitrogenous bodies undergo? 1172. What 
office do plants perform in the daytime? What change occurs at night? To 



414 PHYSIOLOGICAL CHEMISTRY. 

CHAPTEE XXVII. 

DYNAMICS OF VEGETABLE GROWTH. 

§ I. The Forces of Organization. 

1174. In the preceding paragraphs we have confined our at- 
tention to the material changes of vegetable growth ; we are now 
to regard it under the dynamic aspect, and take account of the 
forces brought into play. 

1175. Hypothesis of Latent Vitality. — Before the establish- 
ment of physiological science upon its present inductive basis, 
when everything was quickly explained by the assumption of an 
all-powerful vital principle, it was held that the germ was poten- 
tially the tree ; that is, that all the vital energies of a vast vege- 
table organism which had been growing perhaps for hundreds of 
years, preexisted in the embryo in a dormant state, and that the 
growth consisted only in the waking up of this latent vitality. This 
absurd doctrine was long since replaced by the kindred notion that 
vital force exists in a dormant condition, not alone in the germ, 
but in all matter capable of becoming organized ; that the germ, 
in attracting to itself the materials of growth and incorporating 
them into the living structure, only calls into activity their latent 
powers, and that the forces, heat, light, &c, are but vital stimulants 
which arouse the torpid energies of carbon, oxygen, hydrogen and 
nitrogen ; the growing cell appropriating the vital force thus set free. 

1176. Later Views, — The progress of our knowledge of forces 
has swept away these assumptions, and shown that the same intel- 
ligible and beautiful principles which we have found in the inorganic 
world, extend also to the organized kingdom ; that the plant is no 
anomaly in nature, but a link in her vast chain of activities, and 
only to be understood in connection with the universal scheme. 
The career of the plant is a constant and admirable illustration of 
the great laws of the conservation and correlation of forces. It is 
now considered that, as the plant absorbs matter from the sur- 
rounding world, so it also absorbs force, and as it changes and 
assimilates that matter into organized and vital forms, so it also 

what extent are they injurious? 1174. How are we now to consider vegetable 
growth ? 1175. What was the old hypothesis of latent vitality? By what was it 
replaced ? 1176. What does our knowledge of forces show ? Of what is the career 



THE FORCES OF ORGANIZATION. 415 

assimilates or converts surrounding forces into organized or vital 
force. Not that the plant deals with matter and force separately, 
for they are inseparable ; but in appropriating matter it appro- 
priates also the forces of which it is the medium. 

1177. Storing of Forces in Nature.— Conditions of matter rep- 
resent quantities of power. The solid state contains the least ; the 
force that melts it is stored up in the liquid; while the gaseous 
form represents a still higher condition of power. These forms 
of matter resemble springs coiled up to successive degrees of ten- 
sion : when relaxed they give back their force. Ice is like the re- 
laxed spring ; water like the spring partially bent, and steam like 
the spring strained to a much higher tension. As the vapor re- 
laxes into water, it gives out the force of elasticity; as it still 
further relaxes into ice, it gives out the force of liquidity (280). 

1178. Organic Bodies Reservoirs of Power. — Organic sub- 
stances, like bent springs, are stores of force, and represent the 
power expended in separating and grouping their atoms. Accord- 
ing to the extent of the organizing process, is the force stored away. 
In acids it is least ; in the starch group it is higher, and in the 
hydrogenated group highest. As the three states of matter con- 
stitute three reservoirs of power, the solid lowest, the liquid 
higher, and the aeriform highest, so organic bodies may be regard- 
ed as a fourth reservoir still higher. Organic substances may fall 
directly to the mineral state, as in open combustion, when their 
force is all given out at once in the intense form of heat and light ; 
or they may descend by the slow steps of decay, when the force 
is gradually released ; or again, they may be transferred to the 
animal system, and give out their power as animal force: but 
in all cases the force produced is precisely the same in amount. 

1179. Source of Germinal Force. — The economy of the plant 
is to store, and not to expend. It is fixed; that is, it never con- 
sumes force by locomotion, and never draws upon its constantly 
accumulating stock, except in time of flowering. In germination 
we saw that the embryo is nourished by the 6tored material of the 
seed. But to effect the transformation and carry on new growth, 
force is required, and this is furnished by destruction of a portion 

of the plant an illustration ? Describe its mode of action. 1177. How are forces 
stored in nature? Give the comparison used. 1178. What is said of organic 
bodies in relation to force? Examples. How may they be regarded? In what 
ways may they lose their force, and what of its amount ? 1179. What is the func- 



416 PHYSIOLOGICAL CHEMISTRY. 

of the organized substance of the seed. The part destroyed gives 
up its force, to be reconsumed by the growing embryo, so that the 
plantlet at first draws upon its prepared stock of force, as well as 
of matter. 

1180. Transferrence of Organic Force. — Nature furnishes 
many other illustrations of this principle, in which the forces re- 
leased in dissolution are immediately utilized in evolution. The 
yeast plant accompanies putrefaction : so the c mould ' that appears 
upon damp, decomposing bodies, and the fungi that grow upon de- 
caying wood, are lower forms of growing vegetation. Thus or- 
ganization springs directly from disorganization. As the fall of 
one arm of a balance raises the other, so the descent of organized 
atoms to the mineral state gives out the force required to raise 
other atoms to the like condition. 

1181. Influence of External Forces. — When its store is con- 
sumed, the embryo opens its leaves to the air and light, and com- 
mences to form organic matter out of mineral substances. This 
requires a vast expenditure of power, for which there is no source 
but the forces of the external world. These are spent in produ- 
cing growth, and are stored up as vital force of the vegetable 
organism. According to the intensity with which these forces act, 
is the vigor of growth. In the tropics, where the temperature is 
high, vegetation is rank and luxuriant, and tribes of plants abound 
which can flourish only in torrid regions. Leaving the equator, 
and proceeding north or south, vegetation becomes less rich, and 
new varieties of plants appear with the declining temperature. 
Going still farther from the equator, as the forces diminish in in- 
tensity the vegetation becomes still more scattered and meagre, 
and toward the poles entirely disappears. The abundance of sub- 
stances which plants produce declines also in the same order. 
Tropical plants abound in various aromatic, medicinal, and coloring 
compounds, which are not yielded by those of higher latitudes. 

1182. Again, in ascending mountains, the same remarkable 
phenomena are observed. Leaving tropical gardens at the base, 
we may, in a single day, ascend to the line of eternal snow, cross- 

tion of the plant? From whence does it obtain force? 1180. Give examples of 
the transferrence of force. What of organization ? 1187. Describe the action of 
the embryo. Where does it obtain vital foree ? What determines the vigor of 
growth ? How is this illustrated ? What is said of the substances produced by- 
plants ? 1182. Give further examples. What is thus proved ? 1183. State the re- 



THE FORCES OF ORGANIZATION. 417 

ing belts of vegetation corresponding to those between the equator 
and the poles. Moreover, in extreme northern regions, where the 
sun shines uninterruptedly for three months and a half, the low 
temperature and brevity of the season are compensated by the 
constant action of the solar forces, causing the vegetable world to 
spring into life as if by magic. That the quantity of force in action 
determines the quantity of organization, is thus proved on the most 
stupendous scale. 

1183. The same fact is further illustrated in the growth of 
different varieties of plants. BorssiXGAri/r found, as a result of 
numerous observations, that from germination to maturity the 
same annual plant receives very nearly the same amount of heat, 
whether grown in the temperate latitudes, or in the tropics. 
If the mean temperature is low, it will require more days to ripen 
than if it were high. 

1184. Vast Force Exercised by the Leaf. — When we look 
upon the luxuriant foliage of the tree, we cannot fail to be im- 
pressed with its beauty, but we hardly suspect that those leaves 
which flutter so lightly in the breeze are engines for the exercise 
of enormous power. Yet such is the fact, for they decompose car- 
bonic acid. The atoms of a pound of carbon rush into union with 
those of oxygen — they fall down the chemical precipice with a 
force sufficient to raise a thousand weights each of a thousand 
pounds, one foot high. This expresses the strength of their at- 
traction for each other, and if they are to be separated, this 
amount of force must be again expended. So powerfully are the 
elements of carbonic acid held in combination, that the chemist 
can only separate them by the double action of a high heat and 
the most powerful affinity; even then, only the carbon is set free, 
the oxygen remaining in a state of combination. But what no 
chemist has ever been able to accomplish, is effected by every green 
leaf and every humble blade of grass ; — they decompose carbonic 
acid at common temperatures, retaining the carbon and setting 
the oxygen free. 

1185. Motive Power of the Plant. — But the leaf cannot 
create the power it exerts. Though a chemical engine of wonder- 
ful efficiency, it is no more self-moving than the steam engine, or 

suit of Boussixgault's researches. 11S4. "What proves that leaves are engines 
of vast power ? Describe the force with which carbon unites with oxygen. 
Compare the power of the chemist and the leaf. 11S5. What cannot the leaf do? 

18* 



418 PHYSIOLOGICAL CHEMISTRY. 

the water wheel. Its motive power is the sunbeam ; and as the 
steam engine moves at a rate proportional to the amount of steam 
supplied, and ceases to go at all if the steam is cut off, so the leaf 
performs its work at a rate proportioned to the intensity of the 
light which falls upon it, and ceases to act if it be withdrawn. 

1186. In total darkness plants cannot grow; if there be but 
little light, they are white, watery, and sickly ; and even in the 
shade, as all have observed, they are feeble and dwarfed. The 
leaf can only decompose carbonic acid in the day time. Plants, 
of course, grow at night ; cells multiply and transform materials 
constantly, but the initial act of organization upon which all else 
depends, the separation of carbon from oxygen, only takes place 
under the influence of the light of the sun. 

1187. The Organizing Region of the Spectrum.--To what por- 
tion of the complex ray is assigned the task of effecting the chemi- 
cal changes of the leaf is an interesting question. Heat, though 
largely absorbed in the organizing process, does not produce this 
effect. It was formerly attributed to the chemical, or actinic 
force, but the admirable researches of Dr. Draper proved that 
this view was erroneous. He placed some green leaves in tubes 
of carbonated water, and so arranged them in the several colors 
of the spectrum as to ascertain, from the amount of carbonic acid 
absorbed and of oxygen liberated, how the decomposing force is 
distributed. The result proved that the change takes place most 
actively in the yellow, orange, and green colors. At the ex- 

• tremes of the spectrum, in the region of greatest heat and greatest 
chemical effect, the action was very feeble, or altogether wanting, 
while the amount of change corresponded to the intensity of Ihe 
illumination. 

§ II. Chemistry of the Sunbeam. 

1188. In classical fable we are told that Prometheus stole a 
spark of celestial fire and warmed into life the earthly body he 
had formed. The mythologic dream was parallel with the truth of 
nature ; — the true Promethean spark is the Sunbeam, which, by 

What is said of its motive power ? 1186. How is this proved ? How does the 
action of leaves during the night differ from that under sunlight ? 1187. What 
question is stated? Describe Dr. Draper's experiment. What did it prove? 



CHEMISTRY OF THE SUNBEAM. 419 

its wonderful alchemy transforms dead matter into organized and 
living forms. 

1189. Extent of Solar Influence.— Not only life, but all the 
grand phenomena of force with which we are familiar upon this 
planet, have their origin in the sun. His radiations govern the 
movements of terrestrial atoms, and in these the movements of 
masses take their rise. Should that body cease to give out ema- 
nations, the earth would speedily lose its heat ; life would disap- 
pear, vapors condense, and liquids congeal. There would still 
be tidal influence, due to the attraction of the dark masses of the 
sun and moon, but, as the ocean would be solid, there could be 
only a slight movement in the atmosphere. There might also be 
volcanic force, due to the earth's central heat, although this too 
has been held as subject to astronomic agency. 

1190. Effects of Solar Heat Alone. — Were the sun to radiate 
heat alone the earth would still remain dark, but the oceans would 
melt, and tides begin to lash the coasts. The atmosphere would 
be rarefied unequally as now ; storms would arise, and there would 
be the motive power of wind. Water would be converted into 
vapor, and condensed into invisible clouds and rain. Streams would 
channel their way to the sea, and falling in cataracts, would give 
rise to water power. The descending floods, bringing down the 
sediment, would gradually lower the continents and fill up the 
oceans, while the tides would gnaw away the shores; the distri- 
bution of land and water would be changed, and there would be 
all the extensive effects of aqueous, geologic agency. 

1191. Furthermore, the ehctrieal conditions of matter would 
be disturbed; tropical tornadoes, and the milder storms of the 
temperate latitudes would be accompanied with thunder and 
lightning; the unequal heating of i he earth in its daily rotation 
would give rise to thermo-electric currents, and these would pro- 
duce magnetism. All these results would flow from solar radia- 
tions quickening the motions of earthly atoms, so that ice would 
change to water, and water to vapor. 

1192. Effect of Increased Solar Action. — If we again suppose 
the energy of solar radiation so exalted that light is emitted with 
heat, the higher phenomena of organization become possible. 

1188. What is the true Promethean spark? 1189. State the extent of solar in- 
fluence. What would follow if the sun should cense to emit ray&l 1190. What u 
it should radiate heat alone? 1191. Mention further results. 1192. What would be 



420 PHYSIOLOGICAL CHEMISTRY. 

"With the introduction of plant germs, the vegetable world would 
be called in to being by the vitalizing chemistry of the sun. The 
animal world, dependent upon the vegetable — consuming its mat- 
ter and its force — could then appear with all its multitudinous 
f)rms of power. The burning of wood and coal would also give 
Steam power. Thus, in addition to all the forms of mechanical 
movement upon earth, its very energies and impulses of life origi- 
nate in the sun. 

1193. The Organic Kingdom a Magazine of Force.— The 
vegetable world, born of the atmosphere, consists of condensed 
gases. The animal world, derived from the vegetable, is also but 
solidified air. So the food that we consume, the clothes that we 
wear, the houses in which we live, the fuel that warms us by the 
fireside — that transports us to distant places with lightning speed, 
and labors for us in a thousand ways, are all nothing but con- 
densed air. The sunbeam is the agent of condensation, and thus 
the organic world presents itself as a vast magazine of solar force. 

1194. So the coal deposits — the carbonized remains of a vege- 
tation which flourished long before man appeared upon the globe, 
were condensed from an atmosphere richer in carbonic acid, and 
perhaps by a more brilliant sun, and yet, this coal, having slum- 
bered in its ancient bed through uncounted eras of time, now comes 
forth to surrender its ethereal agents, light and heat, and return as 
carbonic acid to the air from whence it came. 

1195. The Sunbeam the Antagonist of Oxygen. — "When treat- 
ing of oxygen it was stated that this element enshrouds the globe 
and tends to unite with and bring all things to rest, so that if the 
earth were left to the action of its own forces, life would quickly 
disappear, and leave the world a desert. But the earth's vegeta- 
tion is the beautiful instrumentality by which this action is arrest- 
ed. The leaves extract poisonous carbonic acid from the air, de- 
prive it of the elements it had seized, and return it again to the 
atmosphere, while the forces which impel these changes are the 
beams of the sun. These are the great Antagonists of oxygen. 
Under its influence organized matter is rent into its elements and 
carried down to the mineral world ; under the influence of the 
solar rays it is again raised to the organized condition. If oxygen 

the effect if light accompanied heat? What thus originate in the sun? 1193, 
•How is the organic world a magazine of force? 1194. What is said of coal? 
1195. What would be the influence of oxygen uncontrolled ? How is its action ar- 



CHEMISTRY OF THE SUNBEAM. 421 

dilapidates they renovate ; if that decomposes and breaks down, 
they construct and build up ; if that is seen in the falling leaf of 
autumn, they are proclaimed in the exuberant foliage and blossoms 
of spring. If oxygen is the mainspring of destruction, wasting, 
burning, consuming all things — the solar rays constitute the 
mighty force of counteraction. They reunite the dissevered ele- 
ments, and substitute development for decay, calling forth a glory 
from desolation, and life and beauty from the very bosom of death. 

1195. It is the Motive Power of the World.— Thus is the 
earth warmed, illumined, magnetized, and vivified by the sun. In 
the fall of the avalanche, the roar of the cataract, and the flow of 
rivers — in the crash of thunder, the glare of lightning, and the 
sweep of tornadoes — in the blaze of conflagration, and the shock 
of battle — in the beauty of flowers, of the rainbow, and the ever 
shifting clouds — in days and seasons, the silent growth of plants, 
and the elastic spring of animals — in the sail-impelled or steam- 
driven ship, and the flying train — in the heavy respiration of the 
laboring steam engine, and the rapid click of the telegraph ; in all 
the myriad manifestations of earthly powder, we behold the trans- 
muted strength of the all-energizing sun. 

1196. Amount of Solar Radiation. — And yet the entire power 
displayed upon the globe is as nothing compared to the vastness of 
of its source. The earth arrests but the g. s o .0*0 <h ooo of the whole 
amount of force that the sun emits. The total heat received by 
the earth would be sufficient to boil but 300 cubic miles of ice- 
cold water per hour, while the entire amount radiated by the 
sun would boil 700,000 million cubic miles of ice water in that 
length of time. The sun is 1,400,000 times larger than the earth, 
yet the force generated upon each square foot of his surface is 
equal to 7,000 horse power per hour. 

1197. Stupendous as is this scale of power, it again sinks into 
insignificance, when we remember that our sun is itself a star 
— that it is but one of the countless millions of suns which fill the 
immeasurable spaces ■ — each a fountain of energy of the same nature 
as that around which we revolve, and upon which we more imme- 
diately depend. Thus in the strictest sense the earth borrows its 
life from the stars. 

rested ? Describe the opposite action of oxygen and of the solar rays. 1195. How 
is the sun the motive power of the world? 1196. State the amount of solar radia- 
tion the earth receives. How does this compare with the entire amount radiated ? 
1197. What fact renders this amount of force comparatively insignificant ? State 



422 PHYSIOLOGICAL CHEMISTRY. 

1198. The Universe Culminates in Life. — If Astronomy has 
revealed to us a universe of unspeakable grandeur, Chemistry has 
linked the mighty mechanism to the course of terrestrial life. 
She teaches us not only that the leaves and flowers are distilled 
from the crystal medium in which they dwell, hut that they are 
tissues woven in the loom of the universe — their warp the subtlest 
ethers of earth, their weft the radiations of the stars : not only 
that the leaf is the crucible of vitality, whose mysterious alchemy 
is interposed between ourselves and death, but that it is the won- 
drous mechanism appointed to receive and gather the life forces 
which God is perpetually pouring through His universe. 

1199. — It is a fine suggestion of Humboldt that if we could 
imagine those movements of the stellar universe which take place 
in long periods to be compressed into a short space of time, and were 
we endowed with telescopic vision to behold them, we should then 
vividly realize that there is nowhere such a thing as rest. The 
stars which we termftxed would be seen all in motion; constella- 
tions drawing together; clusters unfolding and condensing; nebulaB 
breaking up and universes melting away — motion in every part of 
the vault of heaven. Could we then be permitted to gaze into the 
living organism upon earth — plant, or animal — we should behold 
a kindred spectacle ; the constituent atoms in ceaseless movement 
—combining and separating — groups dissolving and rearranging, 
and all circulating in orderly and determined paths — movement in 
every point of the vital organism. Thus the motions of the ever- 
lasting suns, shot in radiant forms across the universe, reappear in 
the movements of organic beings. The unity of the scheme is un- 
broken—the harmonies of earthly life are but cadences of the 
4 music of the spheres.' 

the nature of celestial radiations. 1198. What is said of Astronomy and Chem- 
istry? What does the latter teach us? 1199. Mention the suggestion of Hum- 
boldt. What should we see in the heavens ? What upon the earth, if we could 
gaze into the living organism ? How is the unity of the scheme preserved ? 1200. 



CHANGES OF FOOD IN THE MOUTH. 423 

CHAPTER XXVIII. 

ANIMAL DIGESTION. 

§ I. Changes of Food in the Mouth. 

1200. — Matter organized by the plant is consumed by the ani- 
mal to form its fabric and maintain its functions. It is to be con- 
verted into blood, the source upon which the whole system draws 
for whatever it requires ; but for this purpose food must be com- 
pletely transformed. No one element of diet contains all the 
necessary materials for the use of the adult ; various articles must 
therefore be mixed. Some of the elements of food are incapable 
of forming blood— these require to be separated. To effect these 
important changes in food is the great purpose of digestion, which 
may be divided into three distinct and successive stages. 

1201. Necessity of Saliva.— As in chemical analysis the first 
step consists in crushing to powder the materials to be acted upon, 
so, at the threshold of the digestive process, we find an admirable 
contrivance for crushing and reducing the food. It consists of a 
double system of teeth, so placed and shaped as to combine cut- 
ting, crushing and grinding, through vertical and side movements 
of the lower jaw, and made to work against each other by power- 
ful muscles. But no amount of mechanical action alone can 
liquefy solid aliment. To do this a solvent is required, and this 
office is performed by the saliva, which is separated from the blood 
and poured into the mouth by three pairs of glands. 

1202. Properties. — The salivary juice is a faintly blue, glairy 
liquid, readily frothing. In health it is always alkaline, from the 
presence of salts of soda, potash and lime, but its alkalinity in- 
creases during and after meals, while in prolonged fasting it be- 
comes almost neutral, and in some inflammatory diseases it is acid. 
It contains an organic principle named ptyalin, an albuminous sub- 
stance very prone to putrefaction. The tartar which collects upon 
the teeth is the residue left by evaporation of the water of the 
saliva, and consists of earthy salts cemented together by animal 
matter. 

What is said of food in connection with blood ? State the purpose of digesfon. 
1201. What of the teeth ? What is the office of the saliva. 1202. Mention the prop- 
erties of the saliva. What is ptyalin ? Tartar ? 1203. Uses of saliva ? Give an 



424 PHYSIOLOGICAL CHEMISTRY. 

1203. Uses. — Saliva serves to lubricate the mouth and moisten 
the food, so that it may assume the pasty condition. It is indis- 
pensable to the sense of taste, as all food is tasteless which the 

. saliva cannot dissolve. It also begins the operation of digestion. 
It converts starch into sugar, and sugar into lactic acid. If a 
little pure starch be chewed for a short time, it will become 
sweet ; a portion of it has been changed to sugar. The importance 
of thoroughly masticating our food, especially the starchy kind, is 
thus apparent. Saliva exerts no digestive action upon the nitro- 
genous aliments. 

§ II. Changes of Food in the Stomach. 

1204. Structure of the Stomach. — The masticated food is car- 
ried by the act of swallowing (deglutition) into the oesophagus (gul- 
let), which conducts it downward into the stomach. This is a pouch- 
shaped enlargement of the digestive tube, with the form shown in 
Fig. 303. The capacity of the human stomach varies, but on an 
average, when moderately distended, it will hold about three 
pints. Its walls consist of three coats ; the outer is known as the 
serous membrane ; the middle consists of two layers of muscular 
bands, and the third is the mucous membrane, which lines its in- 
ternal surface, and is of much greater extent than the outer coats. 

*_ „_ 1205. Mechanism of Secretion. — When 

Fig. 301. 

the lining membrane of the stomach is mag- 
nified about TO diameters, the mucous mem- 
brane exhibits the honeycomb appearance 
seen in Fig. 301. Into these reticulated spaces 
there open little cup-shaped cavities called 
stomach follicles, which are about ^io 0I% an 
inch in diameter. Fig. 302 represents the 
Inner Coat of stomach, magnified secreting follicles from the stomach 

magnified. -. , 

of a dog ; c a the mouths opening upon the 

surface ; e f the closed tubes imbedded in the membrane below. 

The walls of these cavities are webbed over with a tissue of most 

delicate blood vessels, carrying streams of blood ; a network of 

veins surrounds their outlets upon the surface of the membrane, 

while nerves innumerable pervade the whole arrangement. 

1206. The office of these follicles is to separate from the blood 

example of its digestive power. 1204. Describe the stomach. 1205. Explain the 




CHANGES OF FOOD IN THE STOMACH. 



425 



Fig. 302. 




Stomach Follicles. 



the digestive fluid of the stomach. This is done by cell growth. 

At the bottom of the cavities, in the little 

tubular roots, cells arise in immense numbers. 

Nourished by the blood, they multiply and 

swell until they are driven up in crowds to the 

surface, where they burst and deliver their 

contents into the stomach. 

1207. The Gastric Juice is a limpid, col- 
orless, and always distinctly acid fluid, secre- 
ted by the cells of the stomach follicles. Its 
acidity is chiefly due to chlorohydric acid, 
though lactic acid is commonly present. It 
contains a nitrogenous body called pepsin, 
or ferment substance, of which but little is 
known. Liebig does not consider it as a pe- 
culiar digestive agent, but as formed of mi- 
nute parts of the mucous membrane of the stomach, separated and 
in a state of decomposition. This substance, acted on by the oxy*- 
gen swallowed in the frothy saliva, excites the digestive fermen- 
tation attributed to pepsin. The composition of the gastric juice 
varies in different kinds of animals, and seems adapted to different 
kinds of food. 

1208. Its Action. — If coagulated white of egg be placed in water 
acidulated with chlorohydric acid, no solvent action takes place at 
common temperatures for a long time, though at 150° a slow dis- 
solving effect begins. But if a little pepsin be added to the liquid, 
the solution goes on actively. An ounce of water, mixed with 
twelve drops of chlorohydric acid and one grain of pepsin, will 
completely dissolve the white of an egg in two hours at the tem- 
perature of the stomach. It acts in the same manner on cheese, 
flesh, and the whole nitrogenous group, but has no solvent power 
on non-nitrogenous matter. Gastric juice, withdrawn from the 
stomach, produces the same effect, though by no means so rapidly 
as in the stomach. 

1209. Peptones. — In digestion nitrogenous matters are not 
only dissolved, but remain dissolved. They seem to be modified in 
some peculiar way, and to this state the name peptone has been 
applied ; thus albumen produces an albumen peptone ; fibrin a 

mechanism of secretion. 1206. Its action. 1207. What is the gastric juice ? How 
does Liebig regard pepsin ? 1208. Describe the action of the* gastric juice. 1209. 



426 PHYSIOLOGICAL CHEMISTRY. 

fibrin peptone, and casein a casein peptone— substances which 
continue dissolved after the solvent is withdrawn. The presence 
of oily substances has been shown to be essential to the formation 
of these products, and therefore to stomach digestion. 

1210. The quantity of gastric juice secreted is very large. The 
hourly destruction of fibrin throughout the system in average 
muscular action has been assumed as 62 grains, and it has been 
found that 20 parts of gastric juice dissolve one part of dry nitro- 
genous matter. To digest this quantity, some 60 or 70 ounces 
are required. It is, however, questionable whether the gastric 
juice is sufficient to dissolve all the nitrogenous matter required 
for the system. 

1211. Motions of the Stomach. — The food, as it enters the 
stomach through the cardiac orifice, Fig. 303, is immediately sub- 
jected to a peculiar movement, by which it is thoroughly intermixed 
with the gastric fluid. This motion is produced by the alternate 
contraction and relaxation of the muscular bands, which produce a 
constant agitation or churning of the alimentary mass. These con- 
tractions cause the food to revolve round the interior of the stom- 
ach in from one to three minutes, but as chymification advances, 
the rapidity of the motion is increased. The combined effect of 
the agitation and of the mingled solvent is to reduce the solid food 
to a uniform pulpy, semi-fluid mass called chyme. 

1212. Limit of Stomach Digestion. — The opinion long enter- 
tained that the stomach is the exclusive seat of digestive changes, 
is now abandoned. We have seen that foods are divided into two 
great classes, based upon essential differences of chemical compo- 
sition, viz. : the nitrogenous and the non-nitrogenous. This dis- 
tinction reappears in digestion. So different are these two kinds 
of aliment that they require totally different, nay opposite agents 
to dissolve them. Digestion commences in the mouth with an al- 
kaline liquid upon the non-nitrogenous portion of the food ; pro- 
ceeding to the stomach, it meets an acid ; the changes begun in 
the mouth are arrested; the alkaline saliva is neutralized, and 
action begins on the nitrogenous compounds. 

1213. Absorption from the Stomach. — The liquefied food en- 
ters the circulating vessels by absorption, and passes into the 

What of peptones ? 1210. What is said of the quantity of gastric juice secreted ? 
1211. Describe the motions of the stomach. What is chyme ? 1212. Is the stomach 
the sole seat of digestion ? What of the nitrogenous and non nitrogenous foods in 



THIRD STAGE OP DIGESTION. 427 

blood. This is proved by the fact that when the outlet of the 
stomach is closed by tying it, water which has been swallowed 
disappears rapidly from the organ, and medicines act upon the 
system almost as promptly as under natural circumstances. In the 
same way portions of sugar, lactic acid, and digested nitrogenous 
substances, pass into the blood by absorption through the stom- 
ach veins. The remainder of the contents gradually oozes through 
the valvular opening that leads into the intestine. 

1214. Why the Stomach does not Digest Itself. — To the ques- 
tion often asked, Why the gastric secretion does not dissolve and 
digest the stomach itself, it has been triumphantly replied that the 
1 vital force ' of the living stomach prevents such a result. But 
Bernaed and others have proved that the vital force offers no such 
resistance. On inserting the hind legs of a live frog into the 
stomach of a dog, through a fistulous opening, the flesh is almost 
as rapidly dissolved as though it did not belong to a living animal. 
The resisting power of the stomach is due to a sheath of mucus, 
and to the continuous formation of protecting cells, called epthe- 
Hum, during the process of digestion. 

§ III. Third Stage of Digestion. 

1215. Intestinal Digestion. — The partially digested food, dis- 
missed from the stomach, enters the duodenum, or first portion of 
the intestinal tract, where the process is finished. The general 
scheme of the digestive tract is represented in Fig. 303. Into the 
duodenum two small tubes or ducts open; one leading from the 
liver and pouring in bile, and the other from the pancreas yielding 
pancreatic juice, the first being much larger in quantity. 

1216. The Bile is formed in the liver from the venous or dark 
blood, and is accumulated as gall or cystic Mle in a sac called the 
gall bladder. Human bile is a bitter, yellowish-green, ropy liquid, 
of a nauseating odor. Its viscidity is due to the presence of 
mucus from the gall bladder, which gives it a tendency to putre- 
faction. Bile contains a small proportion of nitrogen and a nota- 
ble amount of sulphur. In constitution it may be regarded as a 
species of soap — a combination of fatty acids with alkalies. 

relation to digestion ? 1213. Kow does food enter the blood ? State the proof. 
1214 Why does not the stomach digest itself? 1215. Describe intestinal 



428 



PHYSIOLOGICAL CHEMISTRY. 



1217. Ox bile consists of two resinous acids combined with 
soda ; the cholic and choleic acids. Taurin is a highly sulphurized 

Fig. 303. 



Liver. 



Gall bladder. 




Stomach. 



Spleen. 



Color- 



Large intestines. — . 



$•--- Small intestines 



Colon. 



Small intestines 



Digestive Tract in Man 

crystalline body, obtainable from bile by the action of acids. 
Cholesterine is a crystallizable, fatty constituent of bile, of which 
it forms only yo.^o o P ar ^ But ^ * s important as, from its insolu- 
bility, when once deposited, it cannot be reabsorbed. Hence, ac- 
cumulating in the gall bladder, it forms the chief ingredient of 
gall stones or biliary calculi. It is a constituent of blood and 
brains. 

1218. The Pancreatic Fluid somewhat resembles the saliva. 



digestion. 1216. What of the bile ? 1217. Of ox bile ? Cholesterine? 1218. What 



THIRD STAGE OF DIGESTION. 421) 

It is alkaline, and rapidly changes starch into sugar ; it serves 
therefore to complete the digestion of amylaceous substances. 
When agitated with oil, it forms a very perfect emulsion, and un- 
doubtedly promotes the absorption of oily bodies. 

1219. Besides the bile and pancreatic fluid, the walls of the 
intestine pour out an intestinal juice. By these three alkaline 
agents the digestion of the mouth is resumed. Starch is rapidly 
changed to sugar, and sugar to lactic acid. Although the secre- 
tions poured into the intestines are all alkaline, yet lactic acid is 
so rapidly produced that the intestinal mass quickly becomes 
acidulous. The conditions are thus furnished for the diges- 
tion of the nitrogenous substances that are not dissolved in the 
stomach. The changed food is here termed chyle, 

1220. Intestinal Absorption.— Those substances which are 
dissolved in water in the intestines are taken up by the veins, 
while the oily and fatty matters, which are less perfectly dis- 
solved, are absorbed by a special arrangement of vessels called 
the lacteals ; these are extremely fine tubes, arising in the intes- 
tinal coats. The liquid which enters the lacteals is white, milk- 
like, and rich in oil. These vessels are gathered into knots or 
glands, so as to be greatly prolonged without consuming space. 
They finally gather into a tube called the thoracic duct, and pour 
their contents into a large vein near the left shoulder, and thus 
into the general circulation. 

1221. The Blood. — The series of changes just described has 
for its object the preparation from the food of a nutritious fluid to 
supply materials of renovation and growth to all parts of the 
body. This fluid is the Hood and the apparatus of tubes (blood 
vessels) by which it is conveyed, is termed the circulatory system. 

1222. In man and the higher animals, the blood is red, being 
of a bright scarlet when taken from the arteries, but of a deep 
purplish hue when drawn from the veins. It is unctuous to the 
touch, has a slightly resinous odor, a saline taste, and an alkaline 
reaction. When first removed from the body, the blood appears 
to the naked eye a uniform red liquid ; but when examined by the 
microscope it is seen to consist of two distinct parts — a clear and 
nearly colorless fluid called the plasma, and an immense number 

is the pancreatic fluid ? 1219. "Explain the completion of digestion. 1220 How is 
intestinal absorption effected ? What of the lacteals, glands, &c. ? 1221. State the 
object of all these changes ? What is the circulatory system ? 1222. Describe the 



430 



PHYSIOLOGICAL CHEMISTRY. 




Microscopical Appearance of 
Blood Discs. 



Fig. 305. 



of minute, rounded red particles floating in this liquid, which are 

known as blood globules, or blood cor- 

FlG. 304. rp, xl • • 

puscles. These vary greatly in size 
and form in different animals. In 
man they are flat discs, which have 



a diameter of about the g^Vo °f 
an inch, and are one fourth as 
thick. The corpuscles consist of 
a thick albuminous membrane call- 
ed globulin, filled with a red color- 
ing matter, termed hematin, in 
which iron is a large element. 

1223. Coagulation. After the 
blood has been removed from the 
body for a short time, it sponta- 
neously coagulates, separating into a dark red jelly, or clot (eras- 
samentum), and a pale colored slimy liquid (serum). Coagulation 

is caused by the change 
of soluble fibrin contained 
in blood to the insoluble 
state. The clot consists of 
fine fibrous threads, en- 
closing the red corpuscles, 
Fig. 305. It was formerly 
supposed to be owing to 
the death of the blood, 
but the same effect is con- 
aft, fibres formed in coagulated blood; c, discs stantly taking place within 
entrapped in the meshes. (Magnified 280 times.) , _. , ,, ■.. . -, 

the body, as the liquid 
fibrin of the blood is deposited to produce solid flesh. As the 
fibrin coagulates it forms a fine network or jelly throughout 
the liquid, which entangles and encloses the red corpuscles. It 
also contains a portion of the serum, which may be removed by 
pressure. The serum consists of water, albumen, fatty matter, 
and various salts. 

1224. Composition. — This varies with age, sex, and the state 
of the individual. The chief constituents of the blood of man, 
according to Becqtterel and Kodier, are as follows : 

blood. Of what does it consist? "What of the corpuscles? 1223. What is 
coagulation? How is it caused? 1224. What are the constituents of blood? 




ANIMAL NUTRITION. 431 

Water, ...... 779.00 

Fibrin, ..... 2.20 

Fatty Matters, ..... 1.60 

Albumen, ..... 69.40 

Blood Corpuscles, .... 141.10 

Extractive Matters, .... 6.80 



Salts, 



CHAPTER XXIX. 

FINAL DESTINATION OF FOOD. 

§1. Animal Nutrition. 

1225. In the present chapter we consider the final uses of food 
— the sequel of the course of chemical changes unfolded in the 
preceding pages. Plant products were divided at the outset into 
two groups, the nitrogenous and the non-nitrogenous. We next 
found a twofold digestion conforming to this distinction, and we 
are now to find that this fundamental difference is observed in 
their ultimate uses. The nitrogenous class serves the purposes of 
nutrition, the formation of structure ; the non-nitrogenous serve 
the purposes of respiration, and are chiefly devoted to the produc- 
tion of animal heat. 

1226. The Living Body a Furnace. — The living body is a reg- 
ulated furnace. Its constituents are combustible : a vital fire is 
sustained in the organism from birth to death, and the inhalation 
of oxygen is the draught by which it is supported. But this com- 
bustion must take place in such a manner that other important 
objects can be accomplished; while heat is to be constantly main- 
tained in ' the house we live in,' the structure must not be burned 
down in the process. 

1227. Nitrogen is incombustible, and lowers the combustibility 
of all compounds into which it enters. Even hydrogen and phos- 
phorus lose their combustibility by union with nitrogen. The 
nitrogen of albuminous compounds, which gives them a low com- 
bustibility, adapts them to form the bodily structures which are to 

1225. What are we now to consider? "What of the distinction between the 
nitrogenous and non-nitrogenous bodies? 1226. How is the living body a fur- 
nace ? What precaution is necessary ? 1227. How does nitrogen influence com- 



432 PHYSIOLOGICAL CHEMISTRY. 

have a certain degree of permanence. What the iron is to the 
stove, the nitrogenous tissues are to the living body ; they enclose 
and retain the non-nitrogenous as fuel. Both the fuel and the 
structure are essentially combustible ; the stove ' burns out ' in 
time, and the bodily tissues waste continually ; but the difference 
between the two is sufficient for the great purposes of the animal 
economy. Liebig- remarks : ' Without the powerful resistance 
which the nitrogenous constituents of the body oppose, beyond 
all other parts, to the action of the air, life could not subsist.' 

1228. Office of Albumen.— When it was discovered that albu- 
minous substances are isomeric and convertible, and that they 
originate in the vegetable kingdom, the problem of animal nutri- 
tion was at once and greatly simplified. Albumen was found to 
be the universal * starting point of animal nutrition — the liquid 
basis of tissue and bodily development. This is strikingly illus- 
trated by the process which takes place in the bird's egg during 
incubation. Under the influence of warmth, and by the action of 
oxygen, which enters through the porous shell — the same condi- 
tions as those which accompany respiration — all the tissues, mem- 
branes, and bones (by the aid of lime from the shell) are devel- 
oped. The foundation material from which they are all • derived 
is albumen, and from this also originate the growth and constant 
reproduction of our own bodies during life. 

1229. Nutrition of the Tissues. — The nutrition of the animal 
structures is, therefore, in a chemical point of view, a very simple 
process ; albumen is changed into fibrin, and fibrin to tissue. Al- 
bumen coagulates into a brittle mass, but fibrin, as we have seen, 
coagulates into tough, thread-like fibres, so that blood in which it 
is dissolved has been very properly called 'liquid flesh.' The re- 
lations of albumen, fibrin, and flesh have been aptly compared to 
those of raw cotton, the spun yarn, and the woven fabric. The 
conversion of albumen into fibrin, which commences in the lacteals 
and continues in the blood, is therefore a simple flesh-forming pro- 
cess. The product necessarily remains in a liquid state, that it 
may be distributed by the circulation into all parts of the system, 
while it gradually coagulates into muscular tissue. Cell growth is 
the instrumentality of change. 

bustibility? State the comparison. What is Liebig's remark? 1228. What 
is the office of albumen? Give the illustration. 1229. Define the nutrition 
of animal tissues. What comparison is used? What of the fibrin formed, 



ANIMAL NUTRITION. 433 

1230. Limit to the Nutritive Power.— -There is no evidence 
that the living system has the power of converting one element 
into another. It may transmute compounds of similar constitution 
one into another, and it can destroy substances by a progressive 
series of changes, giving rise to new products at each descending 
step. But it can neither work upward, like the plant, nor com- 
bine for its own use materials that are present. The dissevered 
constituents of used-up tissues exist in the blood, but it is entirely 
incapable of reconverting them into tissue. Nor has the body the 
power of transmuting the non-nitrogenous group into the nutritive, 
or of enabling the former to replace the latter in the exigences of 
the animal economy. It cannot make starch do the work of glu- 
ten. That nutrition consists essentially in the assimilation of al- 
buminous bodies, is now one of the best established principles of 
physiology. 

1231. Yet the respiratory substances, though incapable of 
forming tissue, may yet essentially aid nutrition : such is the case 
with the fats. If the conversion of albumen into fibrin is incom- 
plete, the tissues are imperfectly nourished. The formation of 
tubercles in the lungs, which gives rise to ' consumption,' is due 
to this cause, as tubercular matter consists of half-formed cells 
and coagulated albumen deposited in the pulmonary tissue. The 
cause of this abortive nutrition is not the lack of sufficient nitro- 
genous matter to nourish tissue, but of some other principle. It 
has been recently maintained that it is due to a deficiency of the 
oily matter which is necessary for the formation of cells, and the 
growth of healthy structure. Cod liver oil and a free use of the 
fatty kinds of diet are recommended for such cases. 

1232. Nitrogenous Diet.-— None of the alimentary principles 
taken alone will support life ; a mixed diet is therefore required. 
But the proportion of the ingredients varies in different circum- 
stances. Severe exercise rapidly consumes the tissues, and neces- 
sitates a diet rich in nitrogenous principles. In childhood there 
is a double demand for these constituents, to supply the constant 
waste and promote growth. Milk, rich in nutrient matters, is the 
food furjiished them by nature, and when replaced it should only 

and of cell growth ? 1230. State the power of the living system. Of what is it in- 
capable? In what does nutrition consist? 1231. What of the respiratory sub- 
stances? How doe3 consumption illustrate their value? State the remedy pro- 
posed. 1232. What is said of the alimentary principles ? Of the food of children ? 
19 



434 PHYSIOLOGICAL CHEMISTRY. 

be by a generous, blood-producing diet such as milk, bread, meat, 
eggs. There is apt to occur in children a deficiency in phosphate 
of lime from the rapid formation of bone, and as the articles just 
mentioned contain an excess of phosphoric acid, lime water is 
often a good addition to their food. 

1233. Respiratory Foods. — The respiratory principles taken 
into the system are either burned at once in the blood fQr the 
production of heat, or they accumulate as fat. The demand for 
them varies with temperature, which depends upon season and 
climate. In summer, or in the tropical regions, where the tem- 
perature of the surrounding air rises nearly if not quite to blood 
heat (98°), there can be but slight necessity for generating heat 
within. Under those circumstances a diet of vegetables and fruits, 
with a low proportion of carbon and hydrogen, is selected by in- 
stinct. On the other hand, in winter or in the polar regions, where 
the temperature falls 100° or 150° below that of the body, a rich, 
heat-producing diet is required, and man instinctively seeks for 
fatty and oily foods. In northern regions blubber and oil are 
consumed in vast quantities. The greater density of the air in 
these cases also increases internal oxidation and the consequent 
heat. 

1234. Nutritive Value of Food. — The first step in determin- 
ing this is to remove the water, which varies in amount from 10 to 
98 per cent, in different kinds of food ; they are thus reduced to the 
same condition. Its nutritive value is then determined by a com- 
parison between the quantities of the two classes of ingredients. 
But the respiratory substances vary in heat-producing effect ; 10 
parts of fat equalling in this respect 24 of starch. By multiplying 
the fat by 2.4 it is reduced to its equivalent in starch. Thus the 
9 per cent, of oil in Indian corn is equal to adding 22 per cent, to 
its real amount of starch. On the contrary, albuminous substances, 
whether in the form of albumen, gluten, or casein, have equal nu- 
tritive powers. Hence, by comparing the nitrogenous constituents 
of food with the respiratory, reduced to the expression for starch, 
we can determine the adaptation of any article of diet to the two 
great functions of the living system. The following taBle from 
Liebig presents the comparison : 

1233. Of the respiratory foods ? How does instinct lead us to select food ? 1234. 
How is the nutritive value of foods determined ? How is milk adapted to the 



ANIMAL NUTRITION. 435 

Nutritive. Respiratory. 



Cow's milk contains, for 


10 


SO 


Human milk " 


10 


40 


Horse beans " 


10 


22 


Peas " 


10 


23 


Fat mutton " 


10 


27 


Fat pork " 
Beef " 


10 


30 


10 


17 


Veal 


10 


1 


Wheat flour " 


10 


46 


Oat meal " 


10 


50 


Rye flour " 


10 


57 


Barley " 


10 


57 


Potatoes (white) " 


10 


86 


Potatoes (blue) " 


10 


115 


Rice " 


10 


123 


Buckwheat " 


10 


130 



The above can be regarded only as an average and approximate 
statement. There is much variation in the proportions of the same 
class of substances, as we see in potatoes, and it must be still 
greater in different samples of the same kind of meat ; nor can any 
such statement be relied upon as of itself a sufficient guide in the 
matter of diet. Still it is useful and rich in suggestions. Milk, 
for example, is the diet of a growing animal. It must furnish ni- 
trogenous material both for current waste and for increased devel- 
opment; hence it abounds in the curdy ingredient. But its prop- 
erties are admirably modified to suit special circumstances. Of 
all the young of the animal world, none lead so quiet a life, or 
advance so slowly to maturity, as the human infant ; therefore hu- 
man milk is less rich in muscle-forming constituents than that of 
animals — the cow, for example, whose young develop more quick- 
ly, and exert themselves much earlier. 

1235. Metamorphosis of Tissue.— Some substances have the 
power of influencing tissue changes without properly participating 
in them. Some increase metamorphosis ; others check it. Com- 
mon salt, for example, and an excess of water, act as hasteners of 
transformation, while alcohol and tea act as arresters of change. 
If we consume those substances which augment waste, it is said 
we require a fuller diet to compensate for the extra loss, or the 
body declines in weight with more rapidity than otherwise. But 
if we employ the arresters of metamorphosis, we save tissue, 



young ? 1235. How do different substances influence physiological changes ? 
What is the effect of water and salt ? Tea and alcohol ? 1236. Why does the sys- 



436 PHYSIOLOGICAL CHEMISTRY. 

and can maintain our nsual strength and weight on a more slender 
diet. The subject requires further elucidation.* 

§ II. Respiration and Circulation. 

1236. Destructive Force in the System. — Separation of the 
body implies its waste ; nutrition presupposes destruction. Ali- 
ment is constantly supplied to the system, because it is constantly 
consumed. The tissue is the seat of a kind of polarity ; waste and 
supply in the healthy adult are equal and opposite forces. 

1237. — As the body does not increase in weight, though mat- 
ter is constantly added to it, the destructive process going on 
within must be sufficiently active to use up and carry away the 
same amount of matter that is supplied through the channels of 
nutrition. The source of this perpetual waste and destruction is 
the act of respiration, by which air is brought into contact with 
every portion of the animal fabric. 

1238. Nature of Respiration. — The relation of animals to the 
atmosphere is of the most direct and vital nature. All the pecu- 
liar processes which take place in the animal structure and which 
we call life, are set in motion and kept in motion by atmos- 
pheric oxygen. Its effect is exerted upon the body through the 
medium of the respiratory organs. The action of oxygen is exactly 
of the same nature in all animals ; but the structure and arrange- 
ment of the respiratory mechanism differ according as they are 
destined to be acted upon by oxygen in the condition of a gas, or 
in a state of solution in water. Animals inhabiting the water have 
their breathing organs outside the body ; in air-breathing animals 
they are within. In marine animals they are termed oroncMa or 
gills, and are composed of feathery filaments, or tufts of blood 
vessels, situated externally, so as to be acted on by air contained 
in the water. The higher animals respire by lungs, which consist 
of membranous bags lodged within the body. They contain mil- 
lions of air cells, which are connected with the atmosphere by the 



* For a much more extended discussion of the physiological effects of food, the 
Student is referred to the author's " Household Science." 

tern require food ? What of its forces ? 1237. What is the extent of the destructive 
force ? Its source ? 1238. What is the relation of oxygen to life ? Its medium ? 
How do the respiratory organs differ ? Describe the gills. Lungs. 1239. How 



RESPIRATION AND CIRCULATION. 



437 



trachea and its branchings, and are surrounded by a delicate mem- 
brane many times more extended than the surface of the body. 

1239. The lungs completely fill the cavity of the chest, so that, 
by the alternate expansion and contraction of the surrounding 
walls and floor, they are correspondingly enlarged and diminished 
in size. The contractile pressure of the chest drives the air out 
(expiration), and when the muscles are relaxed, the external pres- 
sure of the atmosphere forces it back again (inspiration). 



Pulmonary 
Artery. 

Heart, 
Right Auricle. 



Right Ventricle. 



Vena Cava. 




Pulmonary 

Vein. 



Left Auricle. 



Left Ventricle. 



Aorta. 



Ideal view of the Circulation in Man. 

1240. Circulation. — Air, entering the lungs, fills and distends 
the numberless little air cells. The enclosing membrane is over- 
spread with the finest network of capillary blood vessels. Pene- 



do the lungs act in breathing ? 1240. Describe the process of circulation. What 



438 



PHYSIOLOGICAL CHEMISTRY. 



trating the membrane, oxygen enters the blood, and, imparting to 
it a bright crimson color, rushes forward with it toward the heart. 
From the heart the blood passes through the arteries to all por- 
tions of the body. These arteries divide and subdivide until they 
are reduced to the finest tubes, which are densely interlaced 
through all parts of the body. As they are distributed through 
the system, they are called systemic capillaries. In these vessels 
the oxygen is changed to carbonic acid, and the arterial blood to 
venous blood. Passing forward, it is gathered into the veins, re- 
turned to the heart, and then driven back to the lungs. Here the 
carbonic acid escapes through the membranes into the air cells ; it 
then diffuses into the bronchial passages and is expelled into the air. 

1241. Fig. 306 is an ideal representation of the double circula- 
tion in man. The fine lines at the top represent the capillaries of 
the lungs; and at the bottom those of the general system. The 
double circulation is shown, and its relation to the heart. The 
vessels on the right side represent the arteries carrying blood 
charged with oxygen, and those on the left side the veins convey- 
ing carbonic acid. 

1242. Oxidation throughout the System.— It was formerly 
supposed that oxygen combined with carbon and hydrogen directly 
in the lungs, but it has been proved that animals respiring pure 
hydrogen or nitrogen continue for some time to exhale carbonic 
acid. A frog was placed in a jar of hydrogen over mercury, 
and continued to expire carbonic acid for eight hours, thus 

showing that the changes do 
not take place immediately 
in the lungs, but throughout 
the system, and are due to 
oxygen previously absorbed. 
The physiological changes 
proceed so sluggishly in rep- 
tiles that they will live long 
in conditions of the atmo- 
sphere which would be 
quickly fatal to higher ani- 
mals. 



Fig. 807. 




Capillary vessels of the Liver. 



are the systemic capillaries ? What are the further changes ? 1241. What does 
Fig. 306 illustrate ? 1242. Where was oxidation formerly supposed to take place ? 
What does the experiment with the frog prove ? What of reptiles ? 1243. What 



RESPIRATION AND CIRCULATION. 439 

1 243.— In the fine blood vessels distributed throughout the body, 
oxygen is constantly changed to carbonic acid, and arterial to ve- 
nous blood. The minuteness of these vessels is surprising. They 
are termed capillary, or hair-like, but they are far smaller than hairs. 
Fig. 307 shows the densely crowded blood vessels on the surface 
of a rabbit's liver, magnified eleven times. Through these won- 
drously fine tubes flows the vital stream, bringing the materials 
of nutrition, bearing away the products of waste, and itself inces- 
santly changing as it presses on. 

1244. Conveyance of Oxygen. — In what manner the blood 
takes up the oxygen and transports it, is not so clearly seen. The 
absorbent power of its water is insufficient. Liebig's suggestion 
that the iron of the blood is the carrier, is unsatisfactory. The 
blood discs are the agents of transportation, and it is probable that 
they hold the oxygen in a peculiarly loose condition of union, sur- 
rendering it at all points to enter into other combinations. 

1245. Gases Absorbed and Exhaled. — Abut 5 per cent, of 
the oxygen inhaled is absorbed by the blood. "When oxygen 
combines with carbon, the bulk of the carbouic acid formed is 
exactly equal to that of the uniting oxygen. If, therefore, all the 
oxygen taken into the system were converted into carbonic acid, 
the amount of this gas exhaled would just equal the oxygen in- 
haled. But this is not the case. The expired breath contains 
on an average about one seventh less than the absorbed oxygen. 
This deficiency combines with hydrogen, and appears in the breath 
as exhaled watery vapor. The bulk of the expired air is greater 
than that inhaled, owing to the presence of moisture and its high 
temperature. 

1246. The average amount of air inspired and exhaled at each 
respiration is 30 cubic inches, and the average number of respira- 
tions 20 per minute, so that 500 cubic feet of air pass through the 
lungs in 24 hours. The amount of carbonic acid exhaled is variable, 
and is interesting as the index of the rate of internal change. The 
more energetic the circulation, the larger the quantity of carbonio 
acid ; it is less during sleep than while awake, and less during 
fasting than after a full meal. 

1 247. How the expired carbonic acid may be measured is shown 

processes go on in the capillaries ? How is their minuteness shown ? 1244. How is 
oxygen probably conveyed ? 1245. What of the gases absorbed ? Of those exhaled ? 
1246. How much air passes through the lungs in 24 hours ? What of the amount of 



440 



PHYSIOLOGICAL CHEMISTRY. 



in Fig. 308. A bird is placed in a bell glass, A, which stands over 
mercury. B is a vessel of water which establishes a current of air 
through the apparatus as its water flows out. The tubes 1 and 2 
contain pumice stone moistened with potash, which absorbs all the 
carbonic acid from the entering air. The bulbs, £7, contain lime wa- 
ter, and the fact that it remains clear proves that the air enters the 
bell glass free from carbonic acid. The air which the bird expires 

Fig. 308. 




Measuring the Carbonic Acid exhaled by a Bird. 

is drawn through the bulbs, D, containing lime water or potash, 
which had been carefully weighed. The carbonic acid exhaled 
by the bird is absorbed, and if the bulbs are again weighed after 
a given time, they indicate the amount of C0 2 exhaled by the bird. 

1248. The Discovery of the Circulation was made upward 
of two hundred years ago by Dr. Haevey, but of its cause he had 
no true idea. This could not be known until the microscope was 
perfected, the capillary mechanism explained, and the sciences of 
chemistry and molecular physics developed. In the absence of 
real knowledge, the circulation of the blood has been ascribed to 
the drawing and driving action of the heart. 

1249. Office of the Heart.— "While it is admitted that the im- 

carbonic acid exhaled. 1247. How is it measured ? 1248. What of Dr. Harvey in 
relation to the circulation of the blood ? What was necessary to explain its cause ? 
To what has it been ascribed ? 1249. To what degree does the heart move the 



RESPIRATION AND CIRCULATION. 441 

pelling action of the heart moves the blood through the large 
tubes, it is equally certain that it cannot drive it through the 
capillaries : the force which acts here is the real cause of the cir- 
culation. There are animals destitute of a heart, but still with a 
definite circulation. Fishes have no heart on the arterial side be- 
tween the lungs (gills) and the systemic capillaries. The heart 
is introduced into the mechanism of the higher and rapidly acting 
animals as a regulator, rather than a motor: it is the beating pen- 
dulum ; the falling weight is to be sought in the capillary system. 

1250. Theory of the Circulation.— Dr. Deapee has given an 
explanation of the causes of the circulation of the blood on physical 
and chemical principles, and brought us nearer to a final solution 
of this interesting problem than any former investigator. We 
have seen how fluids rise in tubes by wetting their sides. "When 
two liquids meet in a tube with unequal affinities for its walls, the 
one having the highest attraction will drive the other before it. 
The arterial blood is charged with oxygen which has a high affin- 
ity for the walls of the capillary tissues. As the oxygen enters 
into combination with the materials it meets with, its affinity is 
satisfied, and arterial is changed to venous blood, which is driven 
forward by the constant pressure of the arterial current behind. 
The circulation is thus immediately due to respiration. Dr. Dra- 
pee applies the same principle to the flow of sap in plants. Water 
of the soil, entering the rootlets and rising through the trunk and 
branches by osmose, passes into the leaf, and is there digested. 
The new gummy, or colloid product has less affinity for the walls 
of the tubes and tissue, and is constantly pushed forward by the 
freshly arriving sap. Tor illustrations of this view, see Deapee's 
Human Physiology. 

1251. Influence of Air. — From the foregoing considerations it 
will be seen that the influence of air is all controlling over the hu- 
man constitution ; it is the first condition of vital activity — the 
immediate impelling power of life. Any one of its elements 
breathed alone would be fatal ; any other proportions would be 
dangerous, but mingled as they are, how bland, how balmy, 
how salutary they become ! It presses upon us with the weight 
of tons ; bathes the sensitive passages, distends the filmy mem- 
blood ? Where is the seat of chief action, and how proved ? What is the function 
of the heart ? 1250. What is said of Dr. Draper's theory ? Explain it. How is it 
elsewhere applied ? 1251. What is said of the influence of air ? 1252. What is stated 

19* 



442 PHYSIOLOGICAL CHEMISTRY. 

branes of the air cells, and flashing through into the blood, is swept 
forward to the inmost depths of the system, corroding and con- 
suming in its progress the living parts ; and yet with such mar- 
vellous delicacy are all these things accomplished, that we re- 
main profoundly unconscious of them. Science has shown that 
there is a deep life-import in these never-ceasing rhythmic move- 
ments of inspiration and expiration, but it can add nothing to 
the simple grandeur of the primeval statement that the Creator 
4 breathed into his nostrils the breath of life, and man became a 
living soul.' 

§ III. Production of Animal Heat. 

1252. All Animals produce Heat. — If water containing animal- 
cules be gradually frozen under a microscope, the last drops seen to 
congeal are those which surround their bodies. From this point 
upward, each class generates an amount of heat peculiar to itself. 
The temperature of the human body may be ascertained by placing 
the bulb of a delicate thermometer under the tongue, but to meas- 
ure more minute quantities of animal heat than this instrument 
can detect, the thermo-electric couple is employed. The action 



Fig. 309. 




Galvanometer for measuring Animal Heat. 

of the latter instrument has already been described. In Fig. 309 
F represents an iron needle bent at the ends and soldered to c c, 
copper wires which are connected with a galvanometer G. As 
long as both points are at the same temperature the needle re- 
mains at rest ; but it moves when the heat of one exceeds that of 
the other. It was desired, for example, to compare the tempera- 
ture of a living and a dead insect. Each was fixed on a stick dd, 
Fig. 310, planted in the earth of a flower pot a. The needles were 

of animal heat ? How is it measured ? 1253. What is said of the heat of the hu- 



PRODUCTION OF ANIMAL HEAT. 



443 



Fig. 310. 




then thrust into corresponding parts of the living and dead insect, 
when the motion of the galvanometer 
indicated the difference of their tem- 
peratures. 

1253. Temperature in Man.— The 
heat of the human body varies hut 
slightly from 98° the world over, though 
the external temperature changes daily 
and hourly, while the variation from 
latitudes and seasons is very great. The 
extremes of equatorial midsummer and 
arctic midwinter embrace a range of 
more than 200°, yet through all these 
thermal vicissitudes the body of a man 
in health deviates but little from the 
constant normal of 98°. 

1254. — In view of these facts it has 
been maintained that the living body Measuring the Heat of insects, 
has some vital, mysterious, internal defence against the influence 
of external agents. But this is erroneous. It is a heated mass 
which has precisely the same relations to surrounding objects 
as any other heated mass. When they are hotter than itself, it 
receives heat ; when they are colder, it loses heat, and the rate of 
heating or cooling depends upon the difference between the tem- 
perature of the body and that of its surrounding medium. But in 
nearly all circumstances the temperature of the body is higher 
than the objects around it ; hence, it is almost constantly losing 
heat by radiation, conduction, and evaporation. 

1255. Nervous Agency. — Animal heat has been ascribed to 
nervous agency, but such an idea^is clearly disproved by what 
takes place in plants. There are two marked periods in the life 
of a plant in which it exercises the heat-evolving function, and 
becomes independent of surrounding temperature. This occurs 
in the germination of seeds and in flowering. A thermometer 
placed in a bunch of arum flowers rose to 121°, when the tem- 
perature of the air was but 60°. As plants have no nervous sys- 
tem, the effect in this case cannot be due to nervous action. The 

man body? 1254. How has it been accounted for? What are the facts in the 
case ? 1255. To what else has animal heat been ascribed ? "What disproves this 
view ? How is it related to the nervous system ? 1256. To what is plant heat 



444 PHYSIOLOGICAL CHEMISTRY. 

production of heat in the animal body is under the control of the 
nervous system probably in the same way that the fire that drives 
the steam engine is under the control of the fireman. 

1256. Cause of the Plant Heat. — In both of the cases referred 
to there is an absorption of oxygen, which unites with the sugar 
of the flower and the oil of the seed, and a liberation of carbonic 
acid in exact proportion. That the heat is due chiefly to oxidation 
is proved by the fact, that when no oxygen is present, heat is not 
evolved ; whereas, if pure oxygen gas is employed, the liberation 
of heat is more rapid than usual. 

1257. Cause of Animal Heat. — The union of oxygen w r ith car- 
bon and hydrogen is a source of heat under varied conditions. 
"We can combine them in no way without producing heat. The 
animal body inhales oxygen and exhales carbonic acid ; there has 
therefore been a union, and that union must have produced heat. 
Here is a real cause, and one adequate to account for nineteen 
twentieths of the heat generated in the body. Muscular and ner- 
vous action produce heat, and this may probably explain the 
source of the deficiency. 

1258. Effect of the Rate of Respiration. — The amount of heat 
generated in an animal is strictly connected with its rate of respi- 
ration, and the amount of oxygen it absorbs. In reptiles and 
fishes the structure of the respiratory organs is such that but a 
small proportion of oxygen is taken into the system. The quan- 
tity of heat produced is therefore small. Their temperature rises 
and falls with that of the surrounding medium, and is never but 
little above it ; hence they are called cold-Hooded animals. The 
respiratory mechanism of birds, on the contrary, is on a most per- 
fect plan ; it works rapidly, and their temperature is consequently 
maintained at a high rate, from 100° to 112°. Infants breathe 
more rapidly than adults, and their temperature is several degrees 
higher. 

1259. Hibernation. — The most striking illustration of the in- 
fluence of respiration over bodily heat is seen in the case of those 
animals which pass the winter season in a state of profound sleep, 
or torpor {hibernation). In this condition the breathing becomes 

chiefly due ? How proved ? 1257. How do you account for animal heat ? What 
of muscular and nervous action ? 1258. With what is the heat connected ? Why 
are reptiles and fishes ' cold-blooded ?' What of birds and infants ? 1259. What 
does hibernation illustrate ? Describe the state. Give some facts in regard to hi- 



PRODUCTION OF ANIMAL POWER. 445 

very slow, the imperfectly oxygenated blood flows sluggishly 
through the heart, and the heat of the animal falls, it may be, al- 
most to the freezing point. The marmot, in summer, is warm- 
blooded ; but as it passes into hibernation, the number of respira- 
tions falls from 500 to 14 in an hour, the pulse at the same time 
sinking from 150 to 15 per minute. An animal in hibernation has 
been placed in an atmosphere of pure carbonic acid and remained 
there four hours without injury, while if thus treated in its active 
condition, it would have perished instantly. 

1260. Spontaneous Combustion. — There has long prevailed an 
opinion that the living body, under some circumstances, might 
take fire and be more or less completely consumed, and many cases 
of this kind are on record. Liebig, however, has demonstrated 
the impossibility of any such result, and affirms that no amount of 
fat, alcohol, or phosphorus which the living body could possibly 
contain, would render it combustible. Upon examination, the 
alleged instances of spontaneous combustion were found to be in 
no case entitled to credence. 

§ IV. Production of Animal Power. 

1261. The amount of thermal force generated annually in the 
body of an adult man is sufficient to raise from 25,000 to 30,000 
lbs. of water from the freezing to the boiling point. All the acts 
of the body, every motion, utterance, breath, or thought consumes 
force. "We make about 9,000,000 separate motions of breathing 
in a year; thereby inhaling and expelling TOO, 000 gallons of air. 
At the same time the heart contracts and dilates 40,000,000 
times — each time with an estimated force of 13 lbs., while thou- 
sands of tons of blood are annually driven through the heart and 
general system. Besides these involuntary acts, the organism gen- 
erates force for a thousand forms of voluntary, physical action. A 
healthy laborer is assumed to be able to exert a force equal to 
raising the weight of his body through 10,000 feet in a day. 

1262. Rate of Physiological Change. — Corresponding to this 
activity is a high rate of internal change. The living body is like 

bernation. 1260. "What is said of spontaneous combustion ? 1261. How much 
heat does a man annually produce? How many motions of breathing? What 
amount of air does he respire ? How many motions of the heart does he make? 
How much force can a laborer exert ? 1262. What amount of food does a man con- 



446 PHYSIOLOGICAL CHEMISTRY. 

a waterfall ; while it appears an unvarying form it is yet composed 
of particles in a state of swift transition. A man coDsumes in a 
year 800 lbs. of solid food, the same amount of oxygen, and about 
1,500 lbs. of water — or altogether a ton and a half of matter. 
Chossat ascertained the waste in various animals to be an average 
of oV of their weight daily, and Schmidt determined it to be, in 
the case of the human being, ^ of the weight. Johnston says : 
4 an animal when fasting will lose from r l T to r V of its whole weight 
in 24 hours'. The waste proceeds so rapidly that the whole human 
body is believed to be renewed in an average period of not more 
than 30 days — the man of eighty years has therefore shifted the 
substance of his corporeal being nearly a thousand times! 

1263. Force Accompanies Change. — In the exercise of func- 
tional power, parts waste and are ever renewed. In all the deep- 
est recesses of the body, in every elastic muscle and conducting 
nerve, and even in the thinking brain, myriads of atoms are con- 
stantly dying and being replaced. As soon as we begin to live 
and act, we begin to die. The decomposition is in proportion to 
the activity. Muscles are rapidly changed, and are always more 
or less acid from the oxidized products in their substance. It 
has been fully proved by G. Yon Liebig that muscles absorb 
oxygen and exhale carbonic acid as long as their contractility 
lasts. "With the exercise of a muscle, blood is urged toward it ; if 
the current is stopped, it is paralyzed. So also with the nervous 
system ; brain power is dependent upon cerebral transformations. 
Indeed changes go forward more rapidly in the brain than in any 
other part, and, while cerebral exercise increases the brainward 
flow, an arrest of the circulation, but for a moment, as in fainting, 
produces unconsciousness. 

1264. Force the Result of Change.— It was formerly held 
that the body acts by virtue of an inherent ' vital property,' and 
that the changes which go on within it are consequences of its ac- 
tivity. This idea was but natural. As Mr. Hinton suggests, if 
man had first met with steam engines in nature he would have 
supposed them endowed with a peculiar c active property,' which 

sume annually? How much oxygen ? Water? In what time does the material 
of the body change? What is said of a man of eighty? 1263. What is the effect 
of exercise? What is the rate of decomposition? The condition of muscles? 
What has Liebig proved? What is said of cerebral changes ? 1264. What was 
formerly held concerning the action of the body? How is this illustrated by the 



PRODUCTION OF ANIMAL POWER. 447 

caused their movement, and when afterward the expansion and 
contraction of the steam was discovered, it would have "been 
looked upon as the result of the 'inherent activity,' and not as its 
cause. It was thus with the animal organism; it was studied 
backward, and effects taken for causes. But science has 
shown that molecular changes are the causes, and not the con- 
sequences of its activity, and that in this respect the living body is 
analogous to the steam engine and the galvanic battery. In the 
steam engine, power results from the oxidation of fuel ; in the 
voltaic battery, from the oxidation of zinc ; in the living body, 
from the oxidation of food and tissue. 

1265. The barbarian explains mechanism by supposing the 
machine to be alive. ' It died last night,' exclaimed the China- 
man in triumph, upon selling the first watch he had ever seen. 
It is only when we begin to discover the beautiful unity of Nature's 
plan that we reverse the primitive notion, and discover the living 
system to be a divinely constructed machine, adapted to the uni- 
versal economy of Nature's forces. It is not strange that men 
were long in perceiving the mechanical relations of the living sys- 
tem, as it is so unlike all other machines in the conditions of 
its action. It consumes itself and repairs itself. i It is as if the 
wheels of the steam engine were made of coal, revolved by their 
own combustion', and grew as fast as they were consumed. 

1266. Analogies of the Living Body and the Steam Engine. 
— These have been traced, in several interesting particulars, as 
follows : 

THE STEAM ENGINE IN ACTION TAKES— THE ANIMAL BODY IN LIFE TAKES— 

1. Fuel — Coal and wood—both com- 1. Food— Vegetables and flesh — 

bustible. both combustible. 

2. Water (for evaporation). 2. Water (for circulation). 

3. Air (for combustion). 3. Air (for respiration). 

AND PRODUCES— AND PRODUCES— 

4. A steady boiling heat of 212° by 4. A steady animal heat of 98° by 

quick combustion. slow combustion. 

5. Smoke, loaded with carbonic acid 5. Expired breath, loaded with car- 

and watery vapor. bonic acid and watery vapor. 

6. Incombustible ash. 6. Incombustible animal refuse. 

steam engine ? To what is the living body analogous in respect to power ? 1265. 
How does the barbarian explain mechanism? When is the opposite view discov- 
ered ? Why were not the mechanical relations of the body not earlier perceived ? 
What is the mechanical peculiarity of the body ? 1266. Mention some points of 



448 PHYSIOLOGICAL CHEMISTRY. 

7. Motive force of simple alternate 7. Motive force Of simple alternate 

push and pull in the piston, contraction and relaxation 

which, acting through wheels, in the muscles which, acting 

bands and levers, does work of through joints, tendons, and 

endless variety. levers, does work of endless 

variety. 

8. A deficiency of fuel, water, or 8. A deficiency of food, drink, or 

air, first disturbs and then air, first disturbs and then 

stops the motion. stops the motion and the life. 

1267. Source of Animal Power. — Like all other machines, 
the living body cannot create power ; it can only convert and use 
the stored force of food. The organic spring that was wound up 
in the plant is relaxed in the animal system, and gives out its 
force as animal power. And here, under the most complex con- 
ditions, we still trace the operation of the great law, that with 
definite material changes are associated determinate quantities 
of force. Moreover, we see how the great dynamic scheme of 
nature is consummated in animal life. Its apparatus is designed 
for the expenditure of power. The strong, bony system is framed 
in parts to admit of free motion ; its hundreds of muscles are the 
instruments of action ; its circulatory system is the fountain of 
force, and its nervous system binds all into a unit for effective 
effort. The energies of the universe are then gathered and 
poured through it for the accomplishment of the purposes to 
which it is destined. 

1268. We have seen that the vegetable kingdom constitutes a 
fourth reservoir of stored force in the plan of nature (1176). Pro- 
fessor Dana holds that the animal is the fifth and highest form of 
'magazined power.' From the immutable or slowly-changing 
granite we rise through more and more changeable forms of 
matter, solid, liquid, gaseous, organic, and reach the summit of the 
scale in the human brain. Dynamically, the rock and the brain 
are nature's opposite poles. The brain is formed of the most un- 
stable materials, consisting of four fifths water, through which is 
diffused the cerebral tissue, with a large proportion of uncoagu- 
lated albumen, phosphorized oils, and other changeable sub- 
stances. So rapid are its transformations, that though but ^ the 
weight of the body, it receives from \ to T V of all the blood driven 
from the heart, to maintain its normal waste and repair. We are 

analogy between the living body and the steam engine. 12G7. What is the source 
of animal power ? How is the animal body related to the universe ? Explain the 
action of its parts. 12G8. How are animals placed in regard to power? What are 
the opposite extremes of power 'i State the composition of the brain. Its weight. 



CYCLES OF ORGANIC NATURE. 449 

to conceive of the brain, therefore, less as a stable organ than as a 
torrent of change, mind being linked not properly with matter, 
but with matter in motion, or in the highest physiological con- 
dition of power. 



CHAPTER XXX. 

CYCLES OF ORGANIC NATURE. 

1269. That matter changes its form and is put by nature to a 
succession of uses has long been vaguely understood. Science has 
given precision to the idea and unfolded a mighty scheme of circu- 
lations and compensations by which the balance and harmony of 
terrestrial affairs is maintained. 

1270. Circulation of Water. — The equilibrium of the world of 
waters is preserved by a vast system of circulations : whenever 
there is movement in one direction, there is counter movement in 
the opposite. From the surface of sea and land water is rising 
incessantly by evaporation into the air, but it all descends in the 
forms of rain, dew and snow, to be again elevated, and again to 
descend, perpetually. 

1271. The rivers which flow into the sea correspond to rivers 
of vapor in the air moving in opposite directions. The water 
which is decomposed by the plant, and, ministering to its trans- 
mutations, is deposited in its structure or its products, is repro- 
duced by the animal, and by the processes of combustion and decay. 
Thus the waters are carried round in constant circles of distilla- 
tion and condensation, of decomposition and recomposition, and 
through this perpetual doing and undoing, the economy of the 
world and the order of life are maintained upon the planet. 

1272. Circulation of Carbon. — In the form of carbonic acid 
this element is withdrawn from the air by plants, and as they 
slowly decay or rapidly burn, the carbon is again resolved into 
carbonic acid and restored to the atmosphere. If the vegetable 
matter is consumed by animals, a like result takes place through 
their respiration and decay. The same interchange goes on in the 
sea, for it must take place wherever there is life. There is a 

Its blood supply. How associated with mind ? 1269. What has science unfolded? 
1270. How is water kept In circulation ? 1271. Describe its changes. 1272. How 



450 PHYSIOLOGICAL CHEMISTEY. 

marine vegetation so near the surface of lakes and oceans that it 
may be acted on by light ; it absorbs carbonic acid from the water, 
decomposes it, and fixes its carbon. Aquatic animals consume it 
and give back carbonic acid by respiration to the watery medium. 

1273. The time required for the complete revolution of these 
chemical wheels varies almost infinitely. "We may consume fruit 
in which the formative processes are actively going on, and its 
sugar will be exhaled from the lungs as carbonic acid, and again 
absorbed by the leaves in perhaps an hour's time. On the other 
hand, the carbon of the coal beds, after slumbering in the earth 
for ages, is but to-day brought forth to be restored as carbonic 
acid to the air. 

1274. Again, many tribes of marine animals form coverings 
of lime and carbonic acid which, accumulating in the course of 
time at the bottom of oceans, are converted into beds of shelly 
limestone. In the warmer parts of the ocean, little insects are 
also busy absorbing the same constituents from the water and 
building up coral reefs which are thousands of miles in extent. 
But is not the carbonic acid absorbed by the ocean, and thus, ap- 
propriated by its animals, chained down forever in the forming 
rocks? So it might well seem did we not know that the eternal 
law of nature is not fixity, but change. The balance that seems 
lost is still preserved, for carbonic acid, liberated in the depths of 
the earth from unknown sources and by processes we can but ob- 
scurely trace, is everywhere rising to the surface. By myriads of 
springs, by volcanoes, both active and extinct, in thousands of 
caves and hollows, in cellars and wells, and from all the soil over 
vast tracts of country, carbonic acid, in incredible volumes, is being 
continually set free and poured into the atmosphere. 

1275. The marvellous perfection and delicacy of these adjust- 
ments become more striking when we consider how small an 
amount of carbon the air contains (570). Notwithstanding the 
prodigious quantities that are poured into and withdrawn from the 
air, this small and precise proportion remains unaltered from age 
to age. Two hundred million tons of coal are now annually con- 
sumed, producing six hundred million tons of carbonic acid. A 
century ago hardly a fraction of this amount was burned, yet the 

is carbon circulated upon land ? Upon the sea ? 1273. What of the time required 
for these changes ? 1274. How are beds of shelly limestone and coral reefs form- 
ed ? In what way is the balance preserved ? 1275. What is said of the amount 



CYCLES OF ORGANIC! NATURE. 451 

enormous supply has not sensibly disturbed the proportion of this 
gas in the atmosphere. 

1276. Circulation of other Elements. — In the same manner 
oxygen and nitrogen are in perpetual movement. Oxygen enters 
the plant in a state of combination ; it is set free, is absorbed by 
the animal, combines with its carbon and hydrogen, is returned 
to the atmosphere, and reentering the plant, goes the rounds again 
and continually. [Nitrogen, taken into the plant as ammonia, is 
converted into gluten, albumen, &c, and then, becoming the food 
of animals, is wrought into their structure. Decomposed and re- 
jected from the animal system, it is again ready to enter the plant. 
Thus, the antagonism of offices between plants and animals, which 
maintains the equilibrium of life, is complete. They may be con- 
trasted in their leading functions as follows : 

THE VEGETABLE THE AXIMAL 

Absorbs carbonic acid from the air. Returns carbonic acid to the air. 

Supplies oxygen to the atmosphere. Withdraws oxygen from the atmos- 
phere. 

Decomposes carbonic acid, water, and Produces carbonic acid, water, and 

ammoniacal salts. ammoniacal salts. 

Produces the organic principles of Consumes the organic principles of 

food. food. 

Endows mineral matter with the prop- Deprives organic matter of the prop- 
erties of life. erties of life. 

Imparts to chemical atoms the prop- Deprives chemical atoms of the prop- 
erty of combustibility. erty of combustibility. 

Imparts to chemical atoms the power Imparts to chemical atoms the power 
of nourishing the animal. of nourishing the vegetable. 

Converts simple into complex com- Converts complex into simple com- 
pounds, pounds. 

Is an apparatus of deoxidation. Is an apparatns of oxidation. 

Is a mechanism of construction. Is a mechanism of reduction. 

Absorbs heat and electricity. Produces heat and electricity. 

1277. And the ethereal atmosphere, so light, so mobile, so at- 
tenuated that it seems almost to connect the worlds of matter and 
of spirit, is the grand theatre of these mighty reactions. It is at once 
the fountain of life and the source of death. From its serene and 
inscrutable depths come the mysterious processions of living beings 
which crowd the earth, and it is the great sepulchre to which they 
all return ; it has received the disrupted and scattered elements 

of carbon in the air ? 1276. Describe the changes of oxygen. Of nitrogen. Men- 
tion some of the points of contrast between plants and animals. 1277. What is 



452 PHYSIOLOGICAL CHEMISTRY. 

of the dead of past generations, and is hourly gathering to itself 
the living of the present. 

1278. Nature a Strict Economist. — Thus the beautiful and the 
unsightly, the noxious and the pure, the great and the small are 
all mingled together, and the same materials are perpetually going 
their rounds of service. The air we breathe and the water we 
drink to-day have been breathed and drunk a thousand times be- 
fore. No material is wasted, no force spent in vain. 

1279. In nothing is the economy of nature more manifest than 
in the connection of the animal races. Matter and force are not 
suffered to run to waste by the death of animals which feed upon 
plants. There are flesh eaters of all grades, from man to the micro- 
scopic infusoria, some of which destroy and eat, while others con- 
sume only the decomposing dead. The putrefaction of animal car- 
casses would be offensive and dangerous, and so numberless insect 
tribes are provided, the larvae of which devour the decomposing 
mass, and are themselves eaten by larger animals. In the aquarium, 
which is a miniature organic world, plants feed animals and ani- 
mals feed plants ; but there must be flesh eaters, for if an animal is 
left to decay, the water becomes foul, and life is arrested. 

1280. Death Essential to the Order of Nature.— Life and 
death are thus bound up indissolubly in the plan of nature. Each 
implies the other ; they are the opposite and equal arms of the or- 
ganic balance. The death of living parts begins with life, and is 
essential to life. ' The creation of a plant was the simultaneous 
institution of life and death — the establishment of an incoming 
and outgoing stream to be in constant flow as long as the king- 
doms of life should last. Vegetable and animal life and death 
are but parts of one idea involved in a single primal plan.' 
(Dana.) 

1281. The Course of Change Irresistible. — Nor is man able 
to arrest the onward course of natural changes, nor by any arts 
can he long withdraw the lifeless forms from the resistless cur- 
rents of circulation. In petty egotism he wraps the bodies of the 
dead in resinous swathings, and places them in massive mauso- 
leums, so that for hundreds, perhaps thousands of years, they may 
be kept from mingling with the restless elements ; but Time at 

the theatre of all these changes ? 1278. What of nature as an economist ? 1279. 
Explain her economy in regard to animals. Where is i I illustrated? 1280. What 
are the mutual relations of life and death ? 1281. What is beyond our power ? Ex- 



CYCLES OF ORGANIC NATURE. 453 

last, in his endless vicissitudes, enters the tomb, and restores the 
forgotten mould to the moving world from whence it came. 

1282. Matter to be Kept Moving.— But though man cannot 
arrest the course of nature, he nevertheless has a control over its 
changes of the highest importance to himself and to society, and 
which involves very grave responsibilities. Air and water, the 
great media of circulation, when they have been used, are designed 
to pass on ; we have no right to them beyond their transient em- 
ployment. They are ours to-day, but to-morrow they belong to all. 
If we detain and suffer them to stagnate around us, they become 
the fruitful instruments of disease and death. The very qualities 
which make them serviceable render them also dangerous. They 
dissolve various ingredients, which are essential to life, or may 
become charged with noxious agents, which are fatal to it. Na- 
ture avenges herself by inflicting fearful penalties upon individuals 
and nations who tamper with and violate her laws. The great 
epidemics, the consuming fevers, the desolating plagues are divine 
admonitions to the wise that the ordinances of nature are not to 
be violated with impunity. 

1283. Conclusion. — And thus our studies lead us to a new 
perception of that sublime lesson of science — the Unity of the 
Universe. The revolutions of the celestial orbs are paralleled by 
the ever-recurring cycles of matter upon earth ; while the energies 
in action obey in both cases the same beneficent but inexorable 
laws. It is the glory of Astronomy to have shown that the har- 
mony of our planetary system is maintained by the eternal war 
of hostile forces, which by their mutual counteraction keep the 
heavenly bodies in their circling paths. Chemistry has shown that 
this great principle is not limited to the field of celestial mechan- 
ism, but that it operates also upon earth, and governs the king- 
doms of terrestrial life. Here too there are conflict and counterac- 
tion—the omnipresent antagonism of warring forces resulting in 
the harmony and stability of the living world ; another illustration 
of that unity of design and harmony of action throughout the 
universe which proclaim the government of One Infinite Mind. 

ample. 1282. How are air and water to be regarded ? What results from their de- 
tention ? Examples. 1283. What great lesson are we taught by Science? What 
has Astronomy proved ? How has Chemistry extended this great principle ? 



INDEX. 



Absorption of heat by gases, 145. 

Acetous fermentation, 381. 

Acids, 67 ; theory of, 273 ; later view of, 

273 ; how formed, 410. 
Acids : 

acetic, 381. 

arsenic, 308. 

aneniouB, 308. 

benzoic, 357. 

boracic, 269. 

butyric, 353. 

caproic, 353. 

caprylic, 353. 

carbolic, 348. 

carbonic, 218. 

chloric, 251. 

chlorohydric, 247. 

chlorous, 252. 

citric, 362. 

cyanic, 226. 

cyaiiohydric, 226. 

cyanuric, 226. 

fluohydric. 254. 

fluosilicic. 268. 

formic, 3S4. 

fulminic, 226. 

gallic, 363. 

gallotannic, 363, 364. 

hippuric, 301. 

hydrochloric, 247. 

hydrofluoric, 254. 

hydrosulphuric, 260. 

hypochlorous, 250. 

iodohydric, 253. 

lactic, 381. 

lithic, 391. 

malic, 362. 

margaric, 350. 

nielissic, 335. 

muriatic. 247. 

nitric. 209. 

nitrous, 209. 

nitro-chlorohydric, 249. 

oleic, 350. 

oxalic, 362. 

pecticj 342. 

perchloric, 252. 

phosphoric, 265. 

prussic, 226. 

pyrogallic, 363. 



Acids : 

pyroligneous, 345. 
silicic, 267. 
stearic, 350. 
sulphuric, 258. 
sulphindigotic. 363. 
sulphurous, 257. 
tannic, 363. 
tartaric, 361. 

Acroleins, 350. 

Actinism. 159. 

Adhesion, 38 ; of liquids to solids, 39 ; of 
gases to liquids, 43 ; influence of on 
boiling point, 123. 

Adipocere, 353. 

Affinity, 57, 58. 

Air, 226 : moisture in, 127 ; relation to ra- 
diant heat, 146 ; weight of. 227 : rare- 
faction of, 229 ; constituents of, 229 ; 
properties of, 231 ; aqueous vapor of, 
231 ; relations to life. 233 ; combustion 
in, 233 ; chemistry of, 235 ; influence 
of. 421. 

Air pump. 227. 

AlbumeD. 370 ; physiological effects of, 
432. 

Albuminous compounds, 370. 

Alchemy, 176. 

Alcohol' 381 ; artificial production of, 
323 : series, 334; methvlic. 345 ; abso- 
lute, 380 ; ethylic, 381 ; amylic, 384. 

Aldehyd. 382. 

Alkalies. 6S ; metals of, 277. 

Alkaiine earths. 276. 

Allotropism, 65, 326. 

Alloys. 317. 

Alum, 294. 

Alumina, 294. 

Aluminum, 293. 

Amalgamation, 85. 

Amalgams, 318. 

Amber. 357. 

Ammonia, 210. 

Ammonium, 288 ; chloride of, 288- 

Amorphism, 49. 

Amylaceous group, 337. 

Anaesthetics, 384. 

Analogy of the living body and steam 
engine, 447. 

Analysis. 56. 

Animal electricity, 101 ; products, 385 ; 
secretion, 389 : digestion, 423 ; nutri- 



456 



INDEX. 



tion, 431 ; "body a furnace, 431 ; heat, 
production of, 442 ; cause of, 443 ; 
power, source of, 447 ; races, depend- 
ence of, 451 ; antagonism of plant 
and animal, 450. 

Antimonial wirie, 309. 

Antimony, 309. 

Antiseptics, 217 ; 374. 

Aqua-ammonia, 211. 

Aqua-regia, 249. 

Aqueous vapor, 230 : relation to radiant 
heat, 147. 

Arabin, 341. 

Architecture of the tree, 408. 

Argand burner, 243. 

Arsenic, 307 ; test of, 308. 

Arseniuretted hydrogen, 308. 

Ashes, 279 ; as a fertilizer, 402. 

Asphaltum, 347. 

Assaying, 315. 

Athermic bodies, 143. 

Atmosphere, the, 226. 

Atmospheric elements, 180. 

Atmospheric pressure, 228. 

Atomic spaces, 37 ; theory, 64 ; heat, 172. 

Atoms, 36 ; movements of, 109. 

Axis of crystals, 54. 

Azote, 207. 

B 

Balance, 31. 

Balsams, 357. 

Barium, 289. 

Barometer, 228. 

Bases, 68 ; organic, 364. 

Battery, Smee's galvanic, 88 ; Daniell's, 
89 ; Grove's, 90 ; Bunsen's carbon, 90 ; 
Maynooth, 91 ; Schonbein's, 91. 

Beer, 378 ; lager, 379. 

Beeswax, 356. 

Benzoin, 357. 

Benzole, 348. 

Berth elot's researches, 322. 

Bile, 427. 

Bismutb, 309. 

Bisulphide of carbon, 261. 

Bitumen, 347. 

Bleaching, 246, 250. 

Blood, 429 ; globules of, 430 ; coagula- 
tion of, 430 ; composition of, 431. 

Blowpipe, common, 243 ; compound, 238. 

Boiling, 122, 123. 

Bones, 388 ; as a fertilizer, 403. 

Borax, 284. 

Boron, 269. 

Brain, 446. 

Brandy, 380. 

Brass, 317. 

Bread making, 392 ; aerated, 393 ; phos- 
phated, 394. 

British gum, 341. 

Bromine, 252. 

Bronze, 318. 

Bruccia, 365 ; burning fluid, 355. 

Buneerfs discoveries, 156. 

Butter, 353. 

C 

Cadmium, 306. 
Caesium, 156, 287. 



Caffeine, 365. 

Calcium, 289. 

Calico printing, 366. 

Calomel, 313. 

Caloric, 107 ; Brewster on, 235. 

Calorimetry, 118. 

Camphene, 355. 

Camphor, 355 ; artificial, 355. 

Candle, burning of, 239. 

Caoutchouc, 357. 

Capillary attraction, 40. 

Carbon, 212; influence of in organic 
compounds, 325. 

Carbonate of lime, 291. 

Carbonate of soda, 283. 

Carbonic acid, test of, 219 ; poisoning by, 
220 ; sources of, 220. 

Carbonic oxide, 221; expiration of, 439. 

Carburetted hydrogen, 198 ; light, 222. 

Carmine, 368. 

Caromel, 338. 

Casein, 372. 

Catalysis, 59. 

Cells, 407. 

Cellulin, 342. 

Cements, 291. 

Charcoal, 216. 

Cheese, 391. 

Chemical attraction, 55. 

Chemical changes, 29. 

Chemical Chart, 61. 

Chemical combination, 60. 

Chemical physics, 29. 

Chemistry of light, 158 ; of the stars, 
161 ; of the sunbeam, 418 ■ of vegeta- 
ble growth, 408. 

Chlorate of potash, 183. 

Chloresterine, 391. 

Chloride of mercury, 313. 

Chloride of sodium, 281. 

Chlorine, 245 ; a disinfectant, 251. 

Chloroform, 384. 

Chlorophyle, 369. 

Choke damp, 218. 

Chromium, 307. 

Chyle, 429. 

Chyme, 426. 

Cinchonine, 364. 

Cinnabar, 313. 

Circuit, voltaic, 84. 

Circulation of blood, 436; course of, 
437 ; discovery of, 440 ; Draper's theo- 
ry of, 441. 

Circulation of matter over the globe, 
448 ; of carbon, 449 ; of oxygen, 445 ; 
of nitrogen, 445. 

Classification, 15. 

Cleavage, 53. 

Coal mineral, 346 ; distillation of, 348 ; 
oil, 348. 

Cobalt, 304. 

Cochineal, 368. 

Coffee, 365. 

Cohesion, 38. 

Coin, 318. 

Coke, 223. 

Collodion, 343. 

Colloid condition of matter, 46, 327. 

Colophony, 356. 



INDEX. 



457 



Coloring principles, 365. 

Colore, cause of, 138. 

Combining numbers, 60. 

Combustion, 233-244 ; spontaneous, 445. 

Common salt, 281. 

Compound radicles, 332. 

Conduction of heat, 114. 

Connection of polarities, 164. 

Connection of the radiant forces, 166. 

Conservation of force, 169. 

Constitution of matter, 35. 

Convection, 116. 

Copper, 310. 

Corrosive sublimate, 313. 

Coupled compounds, 337. 

Cream of tartar, 361. 

Creosote, 345. 

Cryophorus, 126. 

Crystallization, 46 ; systems of, 52. 

Crystals, forms of, 50 ; transformations 

of, 53 ; modes of production, 47. 
Culinary paradox, 123. 
Cupellation, 314. 
Cyanogen, 225. 
Cycles of organic matter, 448. 



Daguerreotype, 319. 

Daniell's battery, 89. 

Death in the order of nature, 451. 

Decay of wood, 345. 

Decrepitation, 276. 

Deliquescence, 276. 

Dew, 143. 

Dextrine, 341. 

Dialysis, 327. 

Diamagnetism, 76. 

Diamond, 213. 

Diathermancy, 143. 

Differential thermometer, 107. 

Diffusion of liquids, 43 •, of gases, 43. 

Digestion in the stomach, 424 ; second 

stage of, 424 ; third stage of, 427. 
Dimorphism, 54. 
Disinfectants, 375. 
Distillation, 130 ; of wood, 344. 
Dobereiner's lamp, 195. 
Drummond light, 239. 
Dyeing, 367. 
Dyes from coal tar, 349. 

E 

Earth's motion, effect of arrest of, 174. 

Ebullition, 122. 

Economy of nature, 451. 

Efflorescence, 276. 

Elastic gum, 357. 

Electric light, 95. 

Electrical hypothesis, 81. 

Electrical induction, 81. 

Electricity, progress of, 72 ; Franklinic, 

77 ; two kinds of, 79 ; a polar force, 80 ; 

sources of, 83 ; voltaic, 83 ; frictional 

and current, 92. 
Electrodes, 85. 
Electro-dynamics, 83. 
Electrolysis, 93. 

20 



Electro-magnetism, 96. 

Electroscope, 79. 

Electrostatics, 77. 

Electrotype, 94. 

Elements, the four ancient, 176 ; the at- 
mospheric, 180. 

Emery, 294. 

Empiricism, 19. 

Energy, potential an actual, 119. 

Epsom salts, 293. 

Equivalents, chemical, 62. 

Equivalents, determining, 331. 

Eremacausis, 187. 

Essential oils, 354. 

Ether, 383. 

Ethereal medium, 137. 

Ethers, fragrant, 385. 

Ethyl, 333. 

Eupion, 344. 

Evaporation, 125 ; of the body as a cool- 
ing agency, 126. 

Expansion, cause of, 109. 

Extractive matter, 369. 



Eats, 349. 

Fermentation, vinous, 376 ; viscous, 380 ; 
acetous, 381. 

Fibrin, 371. 

Filtration, 45. 

Fire, ancient idea of, 233. 

Fixed oils, 349. 

Flame, nature of. 238 ; structure of, 240 ; 
of the blowpipe, 243. 

Flesh, composition of, 385. 

Flesh juice, 386. 

Flowers in ice, 198. 

Fluorescence, 168. 

Fluorine, 254. 

Food, chemistry of, 392. 

Force, illustrations of, 28 ; physical, 28 ; 
ideas of progressive, 164 ; conservation 
of, 169 ; convertibility of, 170 ; persis- 
tence of, 170 ; the result of change, 
446. 

Forces of spectrum, 167. 

Formulas, 69 ; calculating, 332. 

Fraunhofer's lines, 154 ; cause of, 158. 

Freezing mixtures, 121. 

Friction a source of heat, 110. 

Furnace, reverberatory, 272. 

Fusel oil, 385. 



Galena, 177, 311. 

Galvanic battery, 88. 

Gas, origin of the term, 181. 

Gases, influence of upon radiant heat, 

146 ; condensation of, 131. 
Gasometer, 223. 
Gastric juice, 425. 
Gelatin, 386. 
Generalization, 15. 
Gerhardt's views, 71. 
Glass, manufacture of, 2S4. 
Glauber salts, 293. 
Glucose, 339. 
Glue, 387. 



458 



INDEX. 



Gluten, 371. 

Glycerin, 350. 

Gold, 315. 

Graphite, 215. 

Gravity, 29. 

Grove's battery, 90. 

Grove's experiment upon light, 171. 

Guano, 391 ; as a fertilizer, 403. 

Gum, 341. 

Gun cotton, 343. 

Gunpowder, 280. 

Gutta pereha, 358. 

Gypsum, 292. 



Hair, 388 ; coloring of, 363. 

Halogens, 244. 

Heat, influences solution, 44 ; expansion 
by, 104 ; nature of, 107 ; sources of, 
110 ; sources of in friction, 112 ; con- 
nection with electricity, 115 ; radiant, 
139 ; exchanges of, 141 ; absorption of 
by gases, 145 ; relation to light, 167, 168 ; 
atomic, 172 ; units of, 172 ; equivalent 
of, 172 ; animal, 444. 

Heat of combustion, cause of, 236. 

Heat rays, sifting of, 144. 

Heliochromy, 320. 

Hematite, 298. 

Homologous series, 333. 

Horny matter, 388. 

Humus, 345. 

Hyalogens, 266. 

Hydrogen, 192. 

Hydrometer, 34. 

Hygrometers, 127. 

Hypothesis, 15. 



Ice, 120 ; of sea water, 198 ; flowers in, 

198. 
Illuminating gas, 223. 
Illumination, 238. 
Imponderable matter, 72. 
India rubber, 357. 
Indigo, 868. 

Induction, 20; electric, 81; magnetic, 101. 
Interference of wave motions, 148 ; of 

light, 149. 
Iodide of potassium, 278. 
Iodine, 253. 
Iron, 296 ; properties of, 300 ; wrought, 

300 ; oxides of, 303. 
Isinglass, 387. 
Isomerism, 65,326. 
Isomorphism, 54. 



Joule's law, 173. 



K 



KakodyT, 385. 

KirchhofFs discoveries, 156. 
Knowledge a growth, 15. 
Koh-i-nof, 214. 
Kyanizing, 375. 



Lac, 356. 

Lacteals, 429. 

Lactose, 339. 

Lamp, Dobereiner's, 195 ; safety, 241. 

Lampblack, 218. 

Latent heat, 117. 

Lead, 311. 

Leather, 388. 

Light, 132 , reflection and refraction of, 
133 ; absorption of, 143, 157 ; interfer- 
ence of, 149 ; polarization of, 150 ; 
chemistry of, 158 ; relations to heat, 
167, 168. 

Light carburetted hydrogen, 222. 

Lignin, 343 ; lignite, 346. 

Lime, 290. 

Lime light, 239. 

Liquefaction, 121. 

Litharge, 311. 

Lithium, 287. 

Litmus, 368. 

Living body a machine, 446. 

Lungs, 436. 

M 

Madder, 368. 

Magnesia, 292. 

Magnesium, 292. 

Magnetism, 73. 

Magnetism and light, 166. 

Magneto-electricity, 100. 

Malt, 378. 

Manganese, 304. 

Manures, 402, 403. 

Marcet's digester, 129. 

Margarin, 351. 

Marsh gas, 202. 

Matches, 264. 

Matter and force, 27. 

Matter indestructible, 27 ; impressibility 

of, 163. 
Meat, 397 ; cooking of, 398 , salted, 399. 
Mercaptans, 385. 
Mercury, 312. 
Metals, general properties of, 270 ; of the 

alkalies, 277. 
Metamorphosis of tissues, 435. 
Microscope, use of, 329. 
Milk, 389 ; as food, 435. 
Minium, 311. 
Molasses, 339. 
Molecular attractions, 38. 
Molecules, 37. 
Mordants, 367. 
Morphia, 365. 
Mortar and cement, 23*. 
Moser's images, 163. 
Mother liquor, 47 ; motLes of vinegar, 

382. 
Motion, universality of, 108. 
Mucilage, 342. 
Mucous membrane, 424. 
Mucus, 391 ; mucin, 391. 
Mutual relations of the forces, 164, 



Naphtha, 347. 
Nascent state, 59. 



N 



INDEX. 



459 



Nature of heat, 107. 

Necessity of the circulation of matter, 
452. 

Nickel, 304. 

Nicotine, 365. 

Nitrate of soda, 284 ; of silver, 314. 

Nitre, 279. 

Nitric acid, 209. 

Nitric oxide, 208. 

Nitrogen, 206. 

Nitrogenous compounds, 370, 431 ; diet, 
433. 

Nitrous oxide, 207. 

Nomenclature, 66. 

Nordhausen sulphuric acid, 260. 

Nutritive power, limit to, 433 ; nutri- 
tion imperfect, 433 ; value of food, 
434. 

O 

Observation, 14. 

Oil, physiological effects of, 433. 

Oils, 349 ; mineral, 347 ; fixed, 349 ; coal, 
348 ; drying, 351 ; castor, 352 ; croton, 
352 ; unctuous, 352 ; cod liver, 352 ; 
colza, 353 ; palm, 353 ; train, 353 ; vol- 
atile, 354; turpentine, 355 ; sylvic, 356- 
fusel, 385. 

Oleaginous group, 349. 

Olefiant gas, 222. 

Olein, 350. 

Opium, 365. 

Ores of iron, 297. 

Organic chemistry, 321. 

Organic compounds, artificial produc- 
tion of, 322 ; constitution of, 324 ; anal- 
ysis of, 329. 

Organogens, 181. 

Osmose, 41 ; of gases, 43 ; a new theory 
of, 328. 

Oxalic acid, 362. 

Oxygen, 181 ; magnetism of, 77 ; discov- 
ery of, 182 ; properties of, 183 : com- 
bustion in, 185 ; relations to life, 1S7 ; 
rate of consumption, 18s ; proportion 
in nature, 189 ; theory of, 191 ; in bodily 
circulation, 439 ; onice of in circula- 
tion, 440. 

Ozone, 190. 



Pancreatic fluid, 428. 

Paper, 343. 

ParafiSn, 345. 

Parchment, 387 ; vegetable, 343. 

Peat bogs. 346. 

Pectin, 342. 

Pepsin, 425. 

Peptones, 425. 

Peroxide of hydrogen, 206. 

Perpetual motion, 170. 

Petroleum, 347. 

Philosopher's stone, 178. 

Phlogiston, 233. 

Phosphorescence, 162, 263. 

Phosphorus, 262. 

Phosphuretted hydrogen, 266. 

Photography, 160, 318. 

Physiological change, rate of, 445. 



Physiological chemistry, 404. 

Pile voltaic, 88. 

Pitch, 344. 

Plants, 401 ; growth of, 405 ; in apart- 
ments, 413. 

Plaster of Paris, 292. 

Platinum, 316. 

Plumbago, 215. 

Pneumatic trough, 184. 

Poisons, 375 ; woorara, 365. 

Polarity of particles, 75. 

Polarity, rise of the idea of, 164. 

Polarization of light, 150. 

Porcelain, 295. 

Porosity of matter, 35. 

Potash, 278 ; carbonate of, 278 ; nitrate 
of, 279. 

Potassium, 277. 

Pottery, 296. 

Precipitation, 45. 

Prevision a test of science, 12. 

Priestley, 181. 

Protein, 372. 

Putrefaction, 373. 

Pyrogens, 181. 

Pyrometer, 107. 

Q 

Quinia, 364 ; quinine, 364. 

R 

Radiant heat, 139. 

Radiants, 132. 

Radiation, 132. 

Radiators, good and bad, 142. 

Refraction, 133 , double, 153. 

Regulation, 122. 

Resins, 356 ; gum, 357. 

Respiration, 436 ; gases absorbed and 
exhaled in, 439 ; influence of over ani- 
mal heat, 443. 

Respirator, 217. 

Respiratory foods, 434. 

Rochelle salt, 362. 

Rosin, 356. 

Rubidium, 156,287. 

Rumford on heat, 173. 

S 
Safety lamp, 241. 
Sal ammoniac, 288. 
Saliva, properties of, 423. 
Saltpetre, 279. 

Salt rock, 144, 281 ; as an antiseptic, 282. 
Salts, 68 ; theory of, 272 ; later view of, 

274. 
Sap of plants, 409 ; circulation of, 441. 
Saponification, 359. 
Saturation, 45. 
Science, nature of, 18 ; why so recent, 

19 ; claims of, 21. 
Science and art, 19. 
Sciences, succession of, 20. 
Selenium, 262. 
Selzer's experiment, 84. 
Shells, 389. 
Silicon, 266. 



460 



INDEX. 



Silver, 313 ; nitrate of, 314 ; chloride of, 

315. 
Singing flame, 195. 
Smee's battery, 88. 
Smelting of metals, 272 ; of iron, 299. 
Snow crystals, 199. 
Soap, 359; varieties of, 360; action of, 

360. 
Soda, 281/ 
Sodium, 381. 

Soil, organic matter of, 346 ; origin of, 400. 
Solar influence, extent of, 419. 
Solar radiation, amount of, 421. 
Solar spectrum, 134. 
Soluble glass, 268. 
Solution, 44. 
Soups, 398. 
Spar, heavy, 289. 
Specific-gravity, 31. 
Specific heat, 118. 
Spectroscope, 155. 
Spectrum, solar, 134 ; thermal, 140 ; 

chemical, 158 ; analysis, 154 ; organiz- 
ing region of, 418. 
Spermaceti, 353. 
Spheroidal state, 124. 
Stalactites, 292. 
Stalagmites, 292. 
Starch, 340. 

Steam, 130 ; superheated, 130. 
Stearin, 351. 
Steel, 302. 
Stomach, 424 ; follicles, 424 ; digestive 

limit of, 426 ; why the stomach does 

not digest itself, 427. 
Stratified discharge, 101. 
Strontium, 289. 
Strychnia, 365. 
Sublimation, 48. 
Substitution, 336. 
Sugar, 337 ; cane, 338 ; grape, 339 ; milk, 

339. 
Sulphate of soda, 283 ; of ammonia, 288 ; 

of lime, 292. 
Sulphur, 255. 

Sulphuretted hydrogen, 260. 
Sulphuric acid, 258. 
Sulphurous acid, 257. 
Sunbeam the antagonist of oxygen, 420 ; 

motive power of the world, 421. 
Symbols, 69. 
Symmetry of forms, 51. 



Talbotype, 320. 

Tannin, 363. 

Tar 344. 

Tartar, 423 ; cream of, 361. 

Tea, 366. 

Teeth, 388 ; action of, 423. 

Telegraph, electro-magnetic, 98. 

Tellurium, 262. 



Temperature, 105 ; in man, 442, 
Thallium, 156 , 312. 
Theory, 18 ; types, 335. 
Thermo-electricity, 98. 
Thermometer, 105 ; Fahrenheit, lO 

differential, 107 ; Breguet's, 171. 
Thermometric scales, 106. 
Thermometries, 103. 
Tin, 306. 

Tissues, nutrition of, 432. 
Topaz, 52. 
Tourmaline, 151. 
Turpentine, 355. 
Transmutation of metals, 178. 
Tyndall on ice, 199. 
Type metal, 318. 

U 

Universe, culmination of, 422. 
Urea, 391. 
Urine, 391. 



Vapor, elastic force of, 129. 

Vaporization, 125. 

Varnish, 357. 

Vegetable acids, 361. 

Vegetable alkaloids, 364. 

Verdigris, 310. 

Vinegar, 382. 

Vitellin, 371. 

Volatile acids, series of, 334. 

Volatile oils, 354. 

Voltaic circuit, 84 ; polarities of, 86. 

Voltaic pile, 88. 

Volume, combination by, 63. 

W 

Washing fluids, 361. 

Water, 196 ; decomposition of, 93 ; com- 
position of, 197 ; unequal expansion of, 
200 ; atomic constitution of, 201 ; Con- 
gress, 201 ; solvent power of, 202 ; min- 
eral, 203 ; impurities of, 205 ; purifica- 
tion of, 205 ; circulation of, 448. 

Wave theory of light, 135. 

Waxy compounds, 356. 

Weighing, 30. 

White lead, 311. 

Wine, 379 ; spirits of, 377. 

Wood spirit, 345. 

Woody fibre, 342. 

Woulfe's bottles, 211. 



Yeast, 377. 

Yellow coloring matters, 368. 



Zinc, 305. 




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the progress of the popularization of Chemistry." 

It illustrates the nature of elements, compounds, affinity, definite 
and multiple proportions, acids, bases, salts, the salt-radical theory, 
double decomposition, deoxidation, combustion and illumination, 
isomerism, compound radicals, and the composition of the proxi- 
mate principles of food. It covers the whole field of Agricultural 
Chemistry, and is invaluable as an aid to public lecturers, to teach- 
ers in class-room recitation, and for reference in the family. The 
mode of using it is explained in the class-book. 

From the late Horace Mann, President ofAntiooh College. 
I think Mr. Youmans is entitled to great credit for the preparation of his Chart, 
because its use will not only facilitate acquisition, but, what is of far greater impor- 
tance, will increase the exactness and precision of the student's elementary ideas. 

From Dr. John W. Draper, Professor of Chemistry in the University oftf. Y. 
Mr. Youmans' Chart seems to me well adapted to communicate to beginners a 
knowledge of the definite combinations of chemical substances, and as a preliminary 
to the use of symbols, to aid them very much in the recollection of the examples it 
contains. It deserves to be introduced into the schools. 

Fron James B. Rogers, Professor of Chemistry in the University of Pennsylvania. 
"We cordially subscribe to the opinion of Professor Draper concerning the valu* 
to beginners of Mr. Youmans' Chemical Chart. 

JOHN TORREY, 
Professor of Chemistry in the College of Physicians & Surgeons> FT. Y. 

WM. H. ELLET, 
Late Professor of Chemistry in Columbia College, S. C. 
JAMES B. ROGERS, 
Professor of Chemistry in the University of Pennsylvania. 
From Benjamin Silliman, LL. D., Professor of Chemistry in Yale College. 
I have hastily examined Mr. Youmans' New Chemical Diagrams or Chart of 
•bemical combinations by the union of the elements in atomic proportions. Th» 
design appears to be an excellent one. 



Familiar Science. 



The Hand-book of Household Science. 

A POPULAR ACCOUNT OF 

Heat, Ligmt, Air, Aliment, and Cleansing, in their Scientific Principles 
and Domestic Applications. 

BY EDWARD L. YOUMANS, M. D. 

12mo. Illustrated. 470 pages. Price, $1 50. 

Various books have been prepared which cross the field of do- 
mestic science at different points, but this is the first work that 
traverses and occupies the whole ground. Hardly a page can be 
opened to that does not convey information interesting and valuable 
to every person who dwells in a house. The work will be found 
not only of high practical utility, but captivating to the student, 
and unequalled in the interest of its recitations. 

From the Superintendent of Public Instruction of the State of Pennsylvania. 
The daily and hourly importance of the topics embraced in the work, their im- 
perious claims upon public attention, and their intimate connection with individual 
and social welfare, together with the compendious arrangement and copions fulness 
of information presented, and the cautious accuracy and precision of statement, make 
it a publication of the highest practical value for both the household and the school. 

Very respectfully yours, 
Prof. Edward L. Youmans. HENRY C. HICKOK. 

From the Superintendent of Schools of the State of New York. 
It embodies scientific information of the highest importance, arranged with much 
care, and so clearly stated that even the ordinary mind can scarcely fail to grasp and 
Tetain the truths it unfolds and illustrates. It would prove a most valuable class-book 
in our high schools, and I am satisfied that an examination into its merits would result 
in its general introduction into such institutions. Very respectfully yours, 

H. H. VAN DYCK, Superintendent Public Instruction. 

From the Springfield Republican. 
It is the work of a man thoroughly scientific and thoroughly practical. It is no ex- 
travagance to say that a mastery of its contents will secure a better knowledge of the 
applications of Chemistry, Physiology, and Natural Philosophy, to life and life's con- 
cerns, than the combined treatises upon these subjects which are usually found in 
our school-rooms. 

From the Detroit Advertiser. 
This is one of the most valuable and important books that has of late been issued 
from the press. It will do more to elevate and connect the ordinary duties of house- 
hold life with the domain of science than any other work yet published. It is so ar- 
ranged that the general reader and the man of science may refer to it with satisfaction ; 
but it is also a book which ought by all means to be introduced in our schools, and 
which every young woman who expects to be any thing more than a doll or parlor 
automaton, should study and become as familiar with as she is with her prayer-book. 

From the Philadelphia Saturday Courier. 
Few persons realize— few persons begin to realize— the importance of thoroughly un- 
derstanding the nature and effects of light, heat, air, and food; yet the value of suck 
knowledge can hardly be overstated. Mr. Youmans' work is the clearest and fullest 
exposition of science in those relations that has yet appeared. School committees and 
persons directly interested in education who have long been searching for a work of 
this kind will rejoice to find the fruit of their quest in this manual. It is a valuable 
book, written for a valuable purpose: the desire to lift our ordinary domestic life into 
the dignity of intelligence, pervades it throughout and tinctures it in the grain. 



Physical Science. 





Natural Philosophy: 

Embracing the most Kecent Discoveries in the Various Branches of 
Physics, and Exhibiting the Application of Scientific Principles in 
Every-day Life. Accompanied with full descriptions of Experi- 
ments, Practical Exercises, and numerous Illustrations. 

BY G. P. QUACKENBOS, A. M. 
12mo. 450 pages. Price $1 25. 
This book, which is illustrated in the most liberal manner, is 
equally adapted for use with or without apparatus. It is dis- 
tinguished 

1. For its remarkable clearness. 

2. For its fullness of illustration. 

3. For its original method of dealing with difficulties. 

4. For its correction of numerous errors heretofore unfortunately stereo- 
typed in School Philosophies. 

5. For its explanation of scientific principles as they appear in every-day 
life. 

6. For its practical application of these principles in questions presented 
for the pupil's solution. 

7. For a signal perspicuity of arrangement. One thing being presented 
at a time and everything in its proper place, the whole is impressed without 
difficulty or, the mind. 

8. For the interest with which .It invests the subject. From the outset, 
the student is fascinated and filled with a desire to fathom the wonders of 
the material world. 

9. For the embodiment of all recent discoveries in the various depart- 
ments of philosophy. Instead of relying on the obsolete authorities that 
have furnished the matter for many of our popular school Philosophies, the 
author has made it his business to acquaint himself with the present state of 
science, and thus produced such a work as is demanded by the progressive 
spirit of the age. 

All who have examined this book commend it in the highest 
terms. 

"Mr. Quackenbos has long been favorably known as a teacher and also a writer of 
educational books. This elementary work on Natural Philosophy strikes us as being 
one of his most useful and happy efforts."—^. Y. Courier and Enquirer. 

" A very complete system. We have been particularly struck with the conciseness 
and intelligible character of the definitions and explanations."— N. Y Observer. 

" It is much the most complete and instructive school-book on Natural Philosophy 
that we have ever seen." — Christian Union, Louisville, Ky. 

" Every reasonable requirement is met in this new work."— Gazette, Pittsburg, Pa. 
" The whole arrangement is decidedly superior to anything of tho Iliad that ever 
fell under our inspection." — Post Hartford, Conn. 

j4 It places the principles and rules of philosophy within the reach of the young stn« 
lent in a most attractive form. 1 '— Evening Transerivt, Boston. 



